ANSI C Standard Library Reference

ANSI C Standard Library

 

void assert(int expression);

Macro used for internal error detection.(Ignored if NDEBUG is defined where is included.) If expression equals zero, message printed on and called to terminate execution. Source filename and line number in message arefrom preprocessor macros __FILE__ and __LINE__.

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int isalnum(int c);

isalpha(c) or isdigit(c)

int isalpha(int c);

isupper(c) or islower(c)

int iscntrl(int c);

is control character. In ASCII, control characters are 0x00 (NUL) to 0x1F (US), and 0x7F (DEL)

int isdigit(int c);

is decimal digit

int isgraph(int c);

is printing character other than space

int islower(int c);

is lower-case letter

int isprint(int c);

is printing character (including space). In ASCII, printing characters are 0x20 (' ') to 0x7E ('~')

int ispunct(int c);

is printing character other than space, letter, digit

int isspace(int c);

is space, formfeed, newline, carriage return, tab, vertical tab

int isupper(int c);

is upper-case letter

int isxdigit(int c);

is hexadecimal digit

int tolower(int c);

return lower-case equivalent

int toupper(int c);

return upper-case equivalent

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object to which certain library functions assign specific positive values on error

code used for domain errors

code used for range errors

Notes:

• other implementation-defined error values are permitted
• to determine the value (if any) assigned to by a library function, a program should assign zero to immediately prior to the function call

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radix of floating-point representations

FLT_ROUNDS

floating-point rounding mode

Where the prefix "FLT" pertains to type float, "DBL" to type double, and "LDBL" to type long double:

FLT_DIG

DBL_DIG

LDBL_DIG

precision (in decimal digits)

FLT_EPSILON

DBL_EPSILON

LDBL_EPSILON

smallest number x such that 1.0 + x != 1.0

FLT_MANT_DIG

DBL_MANT_DIG

LDBL_MANT_DIG

number of digits, base , in mantissa

FLT_MAX

DBL_MAX

LDBL_MAX

maximum number

FLT_MAX_EXP

DBL_MAX_EXP

LDBL_MAX_EXP

largest positive integer exponent to which can be raised and remain representable

FLT_MIN

DBL_MIN

LDBL_MIN

minimum normalised number

FLT_MIN_EXP

DBL_MIN_EXP

LDBL_MIN_EXP

smallest negative integer exponent to which can be raised and remain representable

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CHAR_BIT

number of bits in a char

CHAR_MAX

maximum value of type char

CHAR_MIN

minimum value of type char

SCHAR_MAX

maximum value of type signed char

SCHAR_MIN

minimum value of type signed char

UCHAR_MAX

maximum value of type unsigned char

SHRT_MAX

maximum value of type short

SHRT_MIN

minimum value of type short

USHRT_MAX

maximum value of type unsigned short

INT_MAX

maximum value of type int

INT_MIN

minimum value of type int

UINT_MAX

maximum value of type unsigned int

maximum value of type long

minimum value of type long

maximum value of type unsigned long

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Describes formatting of monetary and other numeric values:

char* ;

decimal point for non-monetary values

char* grouping;

sizes of digit groups for non-monetary values

char* thousands_sep;

separator for digit groups for non-monetary values (left of "decimal point")

char* currency_symbol;

currency symbol

char* int_curr_symbol;

international currency symbol

char* mon_decimal_point;

decimal point for monetary values

char* mon_grouping;

sizes of digit groups for monetary values

char* mon_thousands_sep;

separator for digit groups for monetary values (left of "decimal point")

char* negative_sign;

negative sign for monetary values

char* positive_sign;

positive sign for monetary values

char frac_digits;

number of digits to be displayed to right of "decimal point" for monetary values

char int_frac_digits;

number of digits to be displayed to right of "decimal point" for international monetary values

char n_cs_precedes;

whether currency symbol precedes (1) or follows (0) negative monetary values

char n_sep_by_space;

whether currency symbol is (1) or is not (0) separated by space from negative monetary values

;

format for negative monetary values:

0

parentheses surround quantity and currency symbol

1

sign precedes quantity and currency symbol

2

sign follows quantity and currency symbol

3

sign immediately precedes currency symbol

4

sign immediately follows currency symbol

char p_cs_precedes;

whether currency symbol precedes (1) or follows (0) positive monetary values

char p_sep_by_space;

whether currency symbol is (1) or is not (0) separated by space from non-negative monetary values

char p_sign_posn;

format for non-negative monetary values, with values as for

Implementations may change field order and include additional fields. Standard C Library functions use only .

* localeconv(void);

returns pointer to formatting information for current locale

char* setlocale(int , const char* locale);

Sets components of locale according to specified and locale. Returns string describing new locale or null on error. (Implementations are permitted to define values of additional to those describe here.)

LC_ALL

argument for all categories

LC_NUMERIC

for numeric formatting information

LC_MONETARY

for monetary formatting information

LC_COLLATE

for information affecting collating functions

LC_CTYPE

for information affecting functions

LC_TIME

for information affecting time conversions functions

NULL

null pointer constant

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On domain error, implementation-defined value returned and set to . On range error, set to and return value is with correct sign for overflow, or zero for underflow. Angles are in radians.

magnitude returned (with correct sign) on overflow error

double exp(double x);

exponential of x

double log(double x);

natural logarithm of x

double log10(double x);

base-10 logarithm of x

double pow(double x, double y);

x raised to power y

double sqrt(double x);

square root of x

double ceil(double x);

smallest integer not less than x

double floor(double x);

largest integer not greater than x

double fabs(double x);

absolute value of x

double ldexp(double x, int n);

x times 2 to the power n

double frexp(double x, int* exp);

if x non-zero, returns value, with absolute value in interval [1/2, 1), and assigns to *exp integer such that product of return value and 2 raised to the power *exp equals x; if x zero, both return value and *exp are zero

double modf(double x, double* ip);

returns fractional part and assigns to *ip integral part of x, both with same sign as x

double fmod(double x, double y);

if y non-zero, floating-point remainder of x/y, with same sign as x; if y zero, result is implementation-defined

double sin(double x);

sine of x

double cos(double x);

cosine of x

double tan(double x);

tangent of x

double asin(double x);

arc-sine of x

double acos(double x);

arc-cosine of x

double atan(double x);

arc-tangent of x

double atan2(double y, double x);

arc-tangent of y/x

double sinh(double x);

hyperbolic sine of x

double cosh(double x);

hyperbolic cosine of x

double tanh(double x);

hyperbolic tangent of x

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type of object holding context information

int setjmp( env);

Saves context information in env and returns zero. Subsequent call to with same env returns non-zero.

void longjmp( env, int val);

Restores context saved by most recent call to with specified env. Execution resumes as a second return from , with returned value val if specified value non-zero, or 1 otherwise.

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abnormal termination

SIGFPE

arithmetic error

SIGILL

invalid execution

SIGINT

(asynchronous) interactive attention

SIGSEGV

illegal storage access

SIGTERM

(asynchronous) termination request

specifies default signal handling

return value indicating error

specifies that signal should be ignored

void (*(int sig, void (*handler)(int)))(int);

Install handler for subsequent signal sig. If handler is , implementation-defined default behaviour will be used; if , signal will be ignored; otherwise function pointed to by handler will be invoked with argument sig. In the last case, handling is restored to default behaviour before handler is called. If handler returns, execution resumes where signal occurred. returns the previous handler or SIG_ERR on error. Initial state is implementation-defined. Implementations may may define signals additional to those listed here.

Sends signal sig. Returns zero on success.

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type of object holding context information

void ( ap, lastarg);

Initialisation macro which must be called once before any unnamed argument is accessed. Stores context information in ap. lastarg is the last named parameter of the function.

type ( ap, type);

Yields value of the type (type) and value of the next unnamed argument.

void ( ap);

Termination macro which must be called once after argument processing and before exit from function.

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NULL

Null pointer constant.

offsetof(stype, m)

Offset (in bytes) of member m from start of structure type stype.

ptrdiff_t

Type for objects declared to store result of subtracting pointers.

size_t

Type for objects declared to store result of sizeof operator.

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Size of buffer used by .

Value used to indicate end-of-stream or to report an error.

FILENAME_MAX

Maximum length required for array of characters to hold a filename.

FOPEN_MAX

Maximum number of files which may be open simultaneously.

Number of characters required for temporary filename generated by .

Null pointer constant.

Value for origin argument to specifying current file position.

Value for origin argument to specifying end of file.

Value for origin argument to specifying beginning of file.

Minimum number of unique filenames generated by calls to .

Value for mode argument to specifying full buffering.

Value for mode argument to specifying line buffering.

Value for mode argument to specifying no buffering.

File pointer for standard input stream. Automatically opened when program execution begins.

File pointer for standard output stream. Automatically opened when program execution begins.

File pointer for standard error stream. Automatically opened when program execution begins.

Type of object holding information necessary to control a stream.

Type for objects declared to store file position information.

Type for objects declared to store result of sizeof operator.

* (const char* filename, const char* mode);

Opens file named filename and returns a stream, or on failure. mode may be one of the following for text files:

"r"

text reading

"w"

text writing

"a"

text append

"r+"

text update (reading and writing)

"w+"

text update, discarding previous content (if any)

"a+"

text append, reading, and writing at end

or one of those strings with b included (after the first character), for binary files.

* freopen(const char* filename, const char* mode, * stream);

Closes file associated with stream, then opens file filename with specified mode and associates it with stream. Returns stream or on error.

int (* stream);

Flushes stream stream and returns zero on success or on error. Effect undefined for input stream. () flushes all output streams.

int (* stream);

Closes stream stream (after flushing, if output stream). Returns on error, zero otherwise.

int (const char* filename);

Removes specified file. Returns non-zero on failure.

int (const char* oldname, const char* newname);

Changes name of file oldname to newname. Returns non-zero on failure.

* ();

Creates temporary file (mode "wb+") which will be removed when closed or on normal program termination. Returns stream or on failure.

char* (char s[]);

Assigns to s (if s non-null) and returns unique name for a temporary file. Unique name is returned for each of the first invocations.

int (* stream, char* buf, int mode, size);

Controls buffering for stream stream. mode is for full buffering, for line buffering, for no buffering. Non-null buf specifies buffer of size size to be used; otherwise, a buffer is allocated. Returns non-zero on error. Call must be before any other operation on stream.

void (* stream, char* buf);

Controls buffering for stream stream. For null buf, turns off buffering, otherwise equivalent to (void)(stream, buf, , ).

int (* stream, const char* format, ...);

Converts (according to format format) and writes output to stream stream. Number of characters written, or negative value on error, is returned. Conversion specifications consist of:

• %
• (optional) flag:

  -

  left adjust

  +

  always sign

  space

  space if no sign

  0

  zero pad

  #

  Alternate form: for conversion character o, first digit will be zero, for [xX], prefix 0x or 0X to non-zero value, for [eEfgG], always decimal point, for [gG]trailing zeros not removed.

• (optional) minimum width: if specified as *, value taken from next argument (which must be int).
• (optional) . (separating width from precision):
• (optional) precision: for conversion character s, maximum characters to be printed from the string, for [eEf], digits after decimal point, for [gG], significant digits, for an integer, minimum number of digits to be printed. If specified as *, value taken from next argument (which must be int).
• (optional) length modifier:

  h

  short or unsigned short

  l

  long or unsigned long

  L

  long double

• conversion character:

  d,i

  int argument, printed in signed decimal notation

  o

  int argument, printed in unsigned octal notation

  x,X

  int argument, printed in unsigned hexadecimal notation

  u

  int argument, printed in unsigned decimal notation

  c

  int argument, printed as single character

  s

  char* argument

  f

  double argument, printed with format [-]mmm.ddd

  e,E

  double argument, printed with format [-]m.dddddd(e|E)(+|-)xx

  g,G

  double argument

  p

  void* argument, printed as pointer

  n

  int* argument : the number of characters written to this point is written into argument

  %

  no argument; prints %

int (const char* format, ...);

(f, ...) is equivalent to(, f, ...)

int (char* s, const char* format, ...);

Like , but output written into string s, which must be large enough to hold the output, rather than to a stream. Output is NUL-terminated. Returns length (excluding the terminating NUL).

int (* stream, const char* format, arg);

Equivalent to with variable argument list replaced by arg, which must have been initialised by the macro (and may have been used in calls to ).

int (const char* format, arg);

Equivalent to with variable argument list replaced by arg, which must have been initialised by the macro (and may have been used in calls to ).

int vsprintf(char* s, const char* format, arg);

Equivalent to with variable argument list replaced by arg, which must have been initialised by the macro (and may have been used in calls to ).

int (* stream, const char* format, ...);

Performs formatted input conversion, reading from stream stream according to format format. The function returns when format is fully processed. Returns number of items converted and assigned, or if end-of-file or error occurs before any conversion. Each of the arguments following format must be a pointer. Format string may contain:

• blanks and tabs, which are ignored
• ordinary characters, which are expected to match next non-white-space of input
• conversion specifications, consisting of:
  • %
  • (optional) assignment suppression character "*"
  • (optional) maximum field width
  • (optional) target width indicator:

    h

    argument is pointer to short rather than int

    l

    argument is pointer to long rather than int, or double rather than float

    L

    argument is pointer to long double rather than float

  • conversion character:

    d

    decimal integer; int* parameter required

    i

    integer; int* parameter required; decimal, octal or hex

    o

    octal integer; int* parameter required

    u

    unsigned decimal integer; unsigned int* parameter required

    x

    hexadecimal integer; int* parameter required

    c

    characters; char* parameter required; white-space is not skipped, and NUL-termination is not performed

    s

    string of non-white-space; char* parameter required; string is NUL-terminated

    e,f,g

    floating-point number; float* parameter required

    p

    pointer value; void* parameter required

    n

    chars read so far; int* parameter required

    [...]

    longest non-empty string from specified set; char* parameter required; string is NUL-terminated

    [^...]

    longest non-empty string not from specified set; char* parameter required; string is NUL-terminated

    %

    literal %; no assignment

int (const char* format, ...);

(f, ...) is equivalent to (, f, ...)

int sscanf(char* s, const char* format, ...);

Like , but input read from string s.

int (* stream);

Returns next character from (input) stream stream, or on end-of-file or error.

char* (char* s, int n, * stream);

Copies characters from (input) stream stream to s, stopping when n-1 characters copied, newline copied, end-of-file reached or error occurs. If no error, s is NUL-terminated. Returns on end-of-file or error, s otherwise.

int (int c, * stream);

Writes c, to stream stream. Returns c, or on error.

char* (const char* s, * stream);

Writes s, to (output) stream stream. Returns non-negative on success or on error.

int (* stream);

Equivalent to except that it may be a macro.

int (void);

Equivalent to ().

char* (char* s);

Copies characters from into s until newline encountered, end-of-file reached, or error occurs. Does not copy newline. NUL-terminates s. Returns s, or on end-of-file or error. Should not be used because of the potential for buffer overflow.

int (int c, * stream);

Equivalent to except that it may be a macro.

int (int c);

putchar(c) is equivalent to (c, ).

int (const char* s);

Writes s (excluding terminating NUL) and a newline to . Returns non-negative on success, on error.

int (int c, * stream);

Pushes c (which must not be ), onto (input) stream stream such that it will be returned by the next read. Only one character of pushback is guaranteed (for each stream). Returns c, or on error.

(void* ptr, size, nobj, * stream);

Reads (at most) nobj objects of size size from stream stream into ptr and returns number of objects read. ( and can be used to check status.)

size_t (const void* ptr, size, nobj, * stream);

Writes to stream stream, nobj objects of size size from array ptr. Returns number of objects written.

int (* stream, long offset, int origin);

Sets file position for stream stream and clears end-of-file indicator. For a binary stream, file position is set to offset bytes from the position indicated by origin: beginning of file for , current position for , or end of file for . Behaviour is similar for a text stream, but offset must be zero or, for only, a value returned by . Returns non-zero on error.

long (* stream);

Returns current file position for stream stream, or -1 on error.

void (* stream);

Equivalent to (stream, 0L, SEEK_SET); (stream).

int (* stream, * ptr);

Stores current file position for stream stream in *ptr. Returns non-zero on error.

int (* stream, const * ptr);

Sets current position of stream stream to *ptr. Returns non-zero on error.

void (* stream);

Clears end-of-file and error indicators for stream stream.

int (* stream);

Returns non-zero if end-of-file indicator is set for stream stream.

int (* stream);

Returns non-zero if error indicator is set for stream stream.

void (const char* s);

Prints s (if non-null) and () to standard error as would:

(, "%s: %s\n", (s !=  ? s : ""), ())

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Value for status argument to indicating failure.

Value for status argument to indicating success.

Maximum value returned by ().

Null pointer constant.

Return type of (). Structure having members:

int quot;

quotient

int rem;

remainder

Return type of (). Structure having members:

long quot;

quotient

long rem;

remainder

Type for objects declared to store result of sizeof operator.

int abs(int n);

long labs(long n);

Returns absolute value of n.

(int num, int denom);

(long num, long denom);

Returns quotient and remainder of num/denom.

double atof(const char* s);

Equivalent to (s, (char**)) except that is not necessarily set on conversion error.

int atoi(const char* s);

Equivalent to (int)(s, (char**), 10) except that is not necessarily set on conversion error.

long atol(const char* s);

Equivalent to (s, (char**), 10) except that is not necessarily set on conversion error.

double (const char* s, char** endp);

Converts initial characters (ignoring leading white space) of s to type double. If endp non-null, stores pointer to unconverted suffix in *endp. On overflow, sets to and returns with the appropriate sign; on underflow, sets to and returns zero; otherwise returns converted value.

long (const char* s, char** endp, int base);

Converts initial characters (ignoring leading white space) of s to type long. If endp non-null, stores pointer to unconverted suffix in *endp. If base between 2 and 36, that base used for conversion; if zero, leading (after any sign) 0X or 0x implies hexadecimal, leading 0 (after any sign) implies octal, otherwise decimal assumed. Leading 0X or 0x permitted for base hexadecimal. On overflow, sets to and returns or (as appropriate for sign); otherwise returns converted value.

unsigned long (const char* s, char** endp, int base);

As for except result is unsigned long and value on overflow is .

void* calloc( nobj, size);

Returns pointer to zero-initialised newly-allocated space for an array of nobj objects each of size size, or on error.

void* malloc( size);

Returns pointer to uninitialised newly-allocated space for an object of size size, or on error.

void* realloc(void* p, size_t size);

Returns pointer to newly-allocated space for an object of size size, initialised, to minimum of old and new sizes, to existing contents of p (if non-null), or on error. On success, old object deallocated, otherwise unchanged.

void free(void* p);

If p non-null, deallocates space to which it points.

void ();

Terminates program abnormally, by calling ().

void (int status);

Terminates program normally. Functions installed using are called (in reverse order to that in which installed), open files are flushed, open streams are closed and control is returned to environment. status is returned to environment in implementation-dependent manner. Zero or indicates successful termination and indicates unsuccessful termination. Implementations may define other values.

int (void (*fcm)(void));

Registers fcn to be called when program terminates normally (or when main returns). Returns non-zero on failure.

int system(const char* s);

If s is not , passes s to environment for execution, and returns status reported by command processor; if s is , non-zero returned if environment has a command processor.

char* getenv(const char* name);

Returns string associated with name name from implementation's environment, or if no such string exists.

void* bsearch(const void* key, const void* base, n, size, int (*cmp)(const void* keyval, const void* datum));

Searches ordered array base (of n objects each of size size) for item matching key according to comparison function cmp. cmp must return negative value if first argument is less than second, zero if equal and positive if greater. Items of base are assumed to be in ascending order (according to cmp). Returns a pointer to an item matching key, or if none found.

void qsort(void* base, n, size, int (*cmp)(const void*, const void*));

Arranges into ascending order array base (of n objects each of size size) according to comparison function cmp. cmp must return negative value if first argument is less than second, zero if equal and positive if greater.

int (void);

Returns pseudo-random number in range 0 to .

void srand(unsigned int seed);

Uses seed as seed for new sequence of pseudo-random numbers. Initial seed is 1.

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Null pointer constant.

Type for objects declared to store result of sizeof operator.

char* strcpy(char* s, const char* ct);

Copies ct to s including terminating NUL and returns s.

char* strncpy(char* s, const char* ct, n);

Copies at most n characters of ct to s. Pads with NUL characters if ct is of length less than n. Note that this may leave s without NUL-termination. Return s.

char* strcat(char* s, const char* ct);

Concatenate ct to s and return s.

char* strncat(char* s, const char* ct, n);

Concatenate at most n characters of ct to s. NUL-terminates s and return it.

int strcmp(const char* cs, const char* ct);

Compares cs with ct, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

int strncmp(const char* cs, const char* ct, n);

Compares at most (the first) n characters of cs and ct, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

int strcoll(const char* cs, const char* ct);

Compares cs with ct according to locale, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

char* strchr(const char* cs, int c);

Returns pointer to first occurrence of c in cs, or if not found.

char* strrchr(const char* cs, int c);

Returns pointer to last occurrence of c in cs, or if not found.

strspn(const char* cs, const char* ct);

Returns length of prefix of cs which consists of characters which are in ct.

strcspn(const char* cs, const char* ct);

Returns length of prefix of cs which consists of characters which are not in ct.

char* strpbrk(const char* cs, const char* ct);

Returns pointer to first occurrence in cs of any character of ct, or if none is found.

char* strstr(const char* cs, const char* ct);

Returns pointer to first occurrence of ct within cs, or if none is found.

strlen(const char* cs);

Returns length of cs.

Returns pointer to implementation-defined message string corresponding with error n.

char* strtok(char* s, const char* t);

Searches s for next token delimited by any character from ct. Non- s indicates the first call of a sequence. If a token is found, it is NUL-terminated and returned, otherwise is returned. ct need not be identical for each call in a sequence.

strxfrm(char* s, const char* ct, n);

Stores in s no more than n characters (including terminating NUL) of a string produced from ct according to a locale-specific transformation. Returns length of entire transformed string.

void* (void* s, const void* ct, n);

Copies n characters from ct to s and returns s. s may be corrupted if objects overlap.

void* memmove(void* s, const void* ct, n);

Copies n characters from ct to s and returns s. s will not be corrupted if objects overlap.

int memcmp(const void* cs, const void* ct, n);

Compares at most (the first) n characters of cs and ct, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

void* memchr(const void* cs, int c, n);

Returns pointer to first occurrence of c in first n characters of cs, or if not found.

void* memset(void* s, int c, n);

Replaces each of the first n characters of s by c and returns s.

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CLOCKS_PER_SEC

The number of units per second.

Null pointer constant.

An arithmetic type elapsed processor representing time.

An arithmetic type representing calendar time.

Represents the components of calendar time:

int tm_sec;

seconds after the minute

int tm_min;

minutes after the hour

int tm_hour;

hours since midnight

int tm_mday;

day of the month

int tm_mon;

months since January

int tm_year;

years since 1900

int tm_wday;

days since Sunday

int tm_yday;

days since January 1

int tm_isdst;

Daylight Saving Time flag : is positive if DST is in effect, zero if not ineffect, negative if information not known.

Implementations may change field order and include additional fields.

clock(void);

Returns elapsed processor time used by program or -1 if not available.

time(* tp);

Returns current calendar time or -1 if not available. If tp is non-, return value is also assigned to *tp.

double difftime( time2, time1);

Returns the difference in seconds between time2 and time1.

mktime(* tp);

If necessary, adjusts fields of *tp to fall withing normal ranges. Returns the corresponding calendar time, or -1 if it cannot be represented.

char* (const * tp);

Returns the given time as a string of the form:
Sun Jan 3 13:08:42 1988\n\0

char* ctime(const * tp);

Returns string equivalent to calendar time tp converted to local time. Equivalent to:
((tp))

* gmtime(const * tp);

Returns calendar time *tp converted to Coordinated Universal Time, or if not available.

* (const * tp);

Returns calendar time *tp converted into localtime.

size_t strftime(char* s, size_t smax, const char* fmt, const * tp);

Formats *tp into s according to fmt. Places no more than smax characters into s, and returns number of characters produced (excluding terminating NUL), or 0 if greater than smax. Formatting conversions (%c) are:

A

name of weekday

a

abbreviated name of weekday

B

name of month

b

abbreviated name of month

c

local date and time representation

d

day of month [01-31]

H

hour (24-hour clock) [00-23]

I

hour (12-hour clock) [01-12]

j

day of year [001-366]

M

minute [00-59]

m

month [01-12]

p

local equivalent of "AM" or "PM"

S

second [00-61]

U

week number of year (Sunday as 1st day of week) [00-53]

W

week number of year (Monday as 1st day of week) [00-53]

w

weekday (Sunday as 0) [0-6]

X

local time representation

x

local date representation

Y

year with century

y

year without century [00-99]

Z

name (if any) of time zone

%

%

[]

---

ANSI C Standard Library

 

void assert(int expression);

Macro used for internal error detection.(Ignored if NDEBUG is defined where is included.) If expression equals zero, message printed on and called to terminate execution. Source filename and line number in message arefrom preprocessor macros __FILE__ and __LINE__.

[]

int isalnum(int c);

isalpha(c) or isdigit(c)

int isalpha(int c);

isupper(c) or islower(c)

int iscntrl(int c);

is control character. In ASCII, control characters are 0x00 (NUL) to 0x1F (US), and 0x7F (DEL)

int isdigit(int c);

is decimal digit

int isgraph(int c);

is printing character other than space

int islower(int c);

is lower-case letter

int isprint(int c);

is printing character (including space). In ASCII, printing characters are 0x20 (' ') to 0x7E ('~')

int ispunct(int c);

is printing character other than space, letter, digit

int isspace(int c);

is space, formfeed, newline, carriage return, tab, vertical tab

int isupper(int c);

is upper-case letter

int isxdigit(int c);

is hexadecimal digit

int tolower(int c);

return lower-case equivalent

int toupper(int c);

return upper-case equivalent

[]

object to which certain library functions assign specific positive values on error

code used for domain errors

code used for range errors

Notes:

• other implementation-defined error values are permitted
• to determine the value (if any) assigned to by a library function, a program should assign zero to immediately prior to the function call

[]

radix of floating-point representations

FLT_ROUNDS

floating-point rounding mode

Where the prefix "FLT" pertains to type float, "DBL" to type double, and "LDBL" to type long double:

FLT_DIG

DBL_DIG

LDBL_DIG

precision (in decimal digits)

FLT_EPSILON

DBL_EPSILON

LDBL_EPSILON

smallest number x such that 1.0 + x != 1.0

FLT_MANT_DIG

DBL_MANT_DIG

LDBL_MANT_DIG

number of digits, base , in mantissa

FLT_MAX

DBL_MAX

LDBL_MAX

maximum number

FLT_MAX_EXP

DBL_MAX_EXP

LDBL_MAX_EXP

largest positive integer exponent to which can be raised and remain representable

FLT_MIN

DBL_MIN

LDBL_MIN

minimum normalised number

FLT_MIN_EXP

DBL_MIN_EXP

LDBL_MIN_EXP

smallest negative integer exponent to which can be raised and remain representable

[]

CHAR_BIT

number of bits in a char

CHAR_MAX

maximum value of type char

CHAR_MIN

minimum value of type char

SCHAR_MAX

maximum value of type signed char

SCHAR_MIN

minimum value of type signed char

UCHAR_MAX

maximum value of type unsigned char

SHRT_MAX

maximum value of type short

SHRT_MIN

minimum value of type short

USHRT_MAX

maximum value of type unsigned short

INT_MAX

maximum value of type int

INT_MIN

minimum value of type int

UINT_MAX

maximum value of type unsigned int

maximum value of type long

minimum value of type long

maximum value of type unsigned long

[]

Describes formatting of monetary and other numeric values:

char* ;

decimal point for non-monetary values

char* grouping;

sizes of digit groups for non-monetary values

char* thousands_sep;

separator for digit groups for non-monetary values (left of "decimal point")

char* currency_symbol;

currency symbol

char* int_curr_symbol;

international currency symbol

char* mon_decimal_point;

decimal point for monetary values

char* mon_grouping;

sizes of digit groups for monetary values

char* mon_thousands_sep;

separator for digit groups for monetary values (left of "decimal point")

char* negative_sign;

negative sign for monetary values

char* positive_sign;

positive sign for monetary values

char frac_digits;

number of digits to be displayed to right of "decimal point" for monetary values

char int_frac_digits;

number of digits to be displayed to right of "decimal point" for international monetary values

char n_cs_precedes;

whether currency symbol precedes (1) or follows (0) negative monetary values

char n_sep_by_space;

whether currency symbol is (1) or is not (0) separated by space from negative monetary values

;

format for negative monetary values:

0

parentheses surround quantity and currency symbol

1

sign precedes quantity and currency symbol

2

sign follows quantity and currency symbol

3

sign immediately precedes currency symbol

4

sign immediately follows currency symbol

char p_cs_precedes;

whether currency symbol precedes (1) or follows (0) positive monetary values

char p_sep_by_space;

whether currency symbol is (1) or is not (0) separated by space from non-negative monetary values

char p_sign_posn;

format for non-negative monetary values, with values as for

Implementations may change field order and include additional fields. Standard C Library functions use only .

* localeconv(void);

returns pointer to formatting information for current locale

char* setlocale(int , const char* locale);

Sets components of locale according to specified and locale. Returns string describing new locale or null on error. (Implementations are permitted to define values of additional to those describe here.)

LC_ALL

argument for all categories

LC_NUMERIC

for numeric formatting information

LC_MONETARY

for monetary formatting information

LC_COLLATE

for information affecting collating functions

LC_CTYPE

for information affecting functions

LC_TIME

for information affecting time conversions functions

NULL

null pointer constant

[]

On domain error, implementation-defined value returned and set to . On range error, set to and return value is with correct sign for overflow, or zero for underflow. Angles are in radians.

magnitude returned (with correct sign) on overflow error

double exp(double x);

exponential of x

double log(double x);

natural logarithm of x

double log10(double x);

base-10 logarithm of x

double pow(double x, double y);

x raised to power y

double sqrt(double x);

square root of x

double ceil(double x);

smallest integer not less than x

double floor(double x);

largest integer not greater than x

double fabs(double x);

absolute value of x

double ldexp(double x, int n);

x times 2 to the power n

double frexp(double x, int* exp);

if x non-zero, returns value, with absolute value in interval [1/2, 1), and assigns to *exp integer such that product of return value and 2 raised to the power *exp equals x; if x zero, both return value and *exp are zero

double modf(double x, double* ip);

returns fractional part and assigns to *ip integral part of x, both with same sign as x

double fmod(double x, double y);

if y non-zero, floating-point remainder of x/y, with same sign as x; if y zero, result is implementation-defined

double sin(double x);

sine of x

double cos(double x);

cosine of x

double tan(double x);

tangent of x

double asin(double x);

arc-sine of x

double acos(double x);

arc-cosine of x

double atan(double x);

arc-tangent of x

double atan2(double y, double x);

arc-tangent of y/x

double sinh(double x);

hyperbolic sine of x

double cosh(double x);

hyperbolic cosine of x

double tanh(double x);

hyperbolic tangent of x

[]

type of object holding context information

int setjmp( env);

Saves context information in env and returns zero. Subsequent call to with same env returns non-zero.

void longjmp( env, int val);

Restores context saved by most recent call to with specified env. Execution resumes as a second return from , with returned value val if specified value non-zero, or 1 otherwise.

[]

abnormal termination

SIGFPE

arithmetic error

SIGILL

invalid execution

SIGINT

(asynchronous) interactive attention

SIGSEGV

illegal storage access

SIGTERM

(asynchronous) termination request

specifies default signal handling

return value indicating error

specifies that signal should be ignored

void (*(int sig, void (*handler)(int)))(int);

Install handler for subsequent signal sig. If handler is , implementation-defined default behaviour will be used; if , signal will be ignored; otherwise function pointed to by handler will be invoked with argument sig. In the last case, handling is restored to default behaviour before handler is called. If handler returns, execution resumes where signal occurred. returns the previous handler or SIG_ERR on error. Initial state is implementation-defined. Implementations may may define signals additional to those listed here.

Sends signal sig. Returns zero on success.

[]

type of object holding context information

void ( ap, lastarg);

Initialisation macro which must be called once before any unnamed argument is accessed. Stores context information in ap. lastarg is the last named parameter of the function.

type ( ap, type);

Yields value of the type (type) and value of the next unnamed argument.

void ( ap);

Termination macro which must be called once after argument processing and before exit from function.

[]

NULL

Null pointer constant.

offsetof(stype, m)

Offset (in bytes) of member m from start of structure type stype.

ptrdiff_t

Type for objects declared to store result of subtracting pointers.

size_t

Type for objects declared to store result of sizeof operator.

[]

Size of buffer used by .

Value used to indicate end-of-stream or to report an error.

FILENAME_MAX

Maximum length required for array of characters to hold a filename.

FOPEN_MAX

Maximum number of files which may be open simultaneously.

Number of characters required for temporary filename generated by .

Null pointer constant.

Value for origin argument to specifying current file position.

Value for origin argument to specifying end of file.

Value for origin argument to specifying beginning of file.

Minimum number of unique filenames generated by calls to .

Value for mode argument to specifying full buffering.

Value for mode argument to specifying line buffering.

Value for mode argument to specifying no buffering.

File pointer for standard input stream. Automatically opened when program execution begins.

File pointer for standard output stream. Automatically opened when program execution begins.

File pointer for standard error stream. Automatically opened when program execution begins.

Type of object holding information necessary to control a stream.

Type for objects declared to store file position information.

Type for objects declared to store result of sizeof operator.

* (const char* filename, const char* mode);

Opens file named filename and returns a stream, or on failure. mode may be one of the following for text files:

"r"

text reading

"w"

text writing

"a"

text append

"r+"

text update (reading and writing)

"w+"

text update, discarding previous content (if any)

"a+"

text append, reading, and writing at end

or one of those strings with b included (after the first character), for binary files.

* freopen(const char* filename, const char* mode, * stream);

Closes file associated with stream, then opens file filename with specified mode and associates it with stream. Returns stream or on error.

int (* stream);

Flushes stream stream and returns zero on success or on error. Effect undefined for input stream. () flushes all output streams.

int (* stream);

Closes stream stream (after flushing, if output stream). Returns on error, zero otherwise.

int (const char* filename);

Removes specified file. Returns non-zero on failure.

int (const char* oldname, const char* newname);

Changes name of file oldname to newname. Returns non-zero on failure.

* ();

Creates temporary file (mode "wb+") which will be removed when closed or on normal program termination. Returns stream or on failure.

char* (char s[]);

Assigns to s (if s non-null) and returns unique name for a temporary file. Unique name is returned for each of the first invocations.

int (* stream, char* buf, int mode, size);

Controls buffering for stream stream. mode is for full buffering, for line buffering, for no buffering. Non-null buf specifies buffer of size size to be used; otherwise, a buffer is allocated. Returns non-zero on error. Call must be before any other operation on stream.

void (* stream, char* buf);

Controls buffering for stream stream. For null buf, turns off buffering, otherwise equivalent to (void)(stream, buf, , ).

int (* stream, const char* format, ...);

Converts (according to format format) and writes output to stream stream. Number of characters written, or negative value on error, is returned. Conversion specifications consist of:

• %
• (optional) flag:

  -

  left adjust

  +

  always sign

  space

  space if no sign

  0

  zero pad

  #

  Alternate form: for conversion character o, first digit will be zero, for [xX], prefix 0x or 0X to non-zero value, for [eEfgG], always decimal point, for [gG]trailing zeros not removed.

• (optional) minimum width: if specified as *, value taken from next argument (which must be int).
• (optional) . (separating width from precision):
• (optional) precision: for conversion character s, maximum characters to be printed from the string, for [eEf], digits after decimal point, for [gG], significant digits, for an integer, minimum number of digits to be printed. If specified as *, value taken from next argument (which must be int).
• (optional) length modifier:

  h

  short or unsigned short

  l

  long or unsigned long

  L

  long double

• conversion character:

  d,i

  int argument, printed in signed decimal notation

  o

  int argument, printed in unsigned octal notation

  x,X

  int argument, printed in unsigned hexadecimal notation

  u

  int argument, printed in unsigned decimal notation

  c

  int argument, printed as single character

  s

  char* argument

  f

  double argument, printed with format [-]mmm.ddd

  e,E

  double argument, printed with format [-]m.dddddd(e|E)(+|-)xx

  g,G

  double argument

  p

  void* argument, printed as pointer

  n

  int* argument : the number of characters written to this point is written into argument

  %

  no argument; prints %

int (const char* format, ...);

(f, ...) is equivalent to(, f, ...)

int (char* s, const char* format, ...);

Like , but output written into string s, which must be large enough to hold the output, rather than to a stream. Output is NUL-terminated. Returns length (excluding the terminating NUL).

int (* stream, const char* format, arg);

Equivalent to with variable argument list replaced by arg, which must have been initialised by the macro (and may have been used in calls to ).

int (const char* format, arg);

Equivalent to with variable argument list replaced by arg, which must have been initialised by the macro (and may have been used in calls to ).

int vsprintf(char* s, const char* format, arg);

Equivalent to with variable argument list replaced by arg, which must have been initialised by the macro (and may have been used in calls to ).

int (* stream, const char* format, ...);

Performs formatted input conversion, reading from stream stream according to format format. The function returns when format is fully processed. Returns number of items converted and assigned, or if end-of-file or error occurs before any conversion. Each of the arguments following format must be a pointer. Format string may contain:

• blanks and tabs, which are ignored
• ordinary characters, which are expected to match next non-white-space of input
• conversion specifications, consisting of:
  • %
  • (optional) assignment suppression character "*"
  • (optional) maximum field width
  • (optional) target width indicator:

    h

    argument is pointer to short rather than int

    l

    argument is pointer to long rather than int, or double rather than float

    L

    argument is pointer to long double rather than float

  • conversion character:

    d

    decimal integer; int* parameter required

    i

    integer; int* parameter required; decimal, octal or hex

    o

    octal integer; int* parameter required

    u

    unsigned decimal integer; unsigned int* parameter required

    x

    hexadecimal integer; int* parameter required

    c

    characters; char* parameter required; white-space is not skipped, and NUL-termination is not performed

    s

    string of non-white-space; char* parameter required; string is NUL-terminated

    e,f,g

    floating-point number; float* parameter required

    p

    pointer value; void* parameter required

    n

    chars read so far; int* parameter required

    [...]

    longest non-empty string from specified set; char* parameter required; string is NUL-terminated

    [^...]

    longest non-empty string not from specified set; char* parameter required; string is NUL-terminated

    %

    literal %; no assignment

int (const char* format, ...);

(f, ...) is equivalent to (, f, ...)

int sscanf(char* s, const char* format, ...);

Like , but input read from string s.

int (* stream);

Returns next character from (input) stream stream, or on end-of-file or error.

char* (char* s, int n, * stream);

Copies characters from (input) stream stream to s, stopping when n-1 characters copied, newline copied, end-of-file reached or error occurs. If no error, s is NUL-terminated. Returns on end-of-file or error, s otherwise.

int (int c, * stream);

Writes c, to stream stream. Returns c, or on error.

char* (const char* s, * stream);

Writes s, to (output) stream stream. Returns non-negative on success or on error.

int (* stream);

Equivalent to except that it may be a macro.

int (void);

Equivalent to ().

char* (char* s);

Copies characters from into s until newline encountered, end-of-file reached, or error occurs. Does not copy newline. NUL-terminates s. Returns s, or on end-of-file or error. Should not be used because of the potential for buffer overflow.

int (int c, * stream);

Equivalent to except that it may be a macro.

int (int c);

putchar(c) is equivalent to (c, ).

int (const char* s);

Writes s (excluding terminating NUL) and a newline to . Returns non-negative on success, on error.

int (int c, * stream);

Pushes c (which must not be ), onto (input) stream stream such that it will be returned by the next read. Only one character of pushback is guaranteed (for each stream). Returns c, or on error.

(void* ptr, size, nobj, * stream);

Reads (at most) nobj objects of size size from stream stream into ptr and returns number of objects read. ( and can be used to check status.)

size_t (const void* ptr, size, nobj, * stream);

Writes to stream stream, nobj objects of size size from array ptr. Returns number of objects written.

int (* stream, long offset, int origin);

Sets file position for stream stream and clears end-of-file indicator. For a binary stream, file position is set to offset bytes from the position indicated by origin: beginning of file for , current position for , or end of file for . Behaviour is similar for a text stream, but offset must be zero or, for only, a value returned by . Returns non-zero on error.

long (* stream);

Returns current file position for stream stream, or -1 on error.

void (* stream);

Equivalent to (stream, 0L, SEEK_SET); (stream).

int (* stream, * ptr);

Stores current file position for stream stream in *ptr. Returns non-zero on error.

int (* stream, const * ptr);

Sets current position of stream stream to *ptr. Returns non-zero on error.

void (* stream);

Clears end-of-file and error indicators for stream stream.

int (* stream);

Returns non-zero if end-of-file indicator is set for stream stream.

int (* stream);

Returns non-zero if error indicator is set for stream stream.

void (const char* s);

Prints s (if non-null) and () to standard error as would:

(, "%s: %s\n", (s !=  ? s : ""), ())

[]

Value for status argument to indicating failure.

Value for status argument to indicating success.

Maximum value returned by ().

Null pointer constant.

Return type of (). Structure having members:

int quot;

quotient

int rem;

remainder

Return type of (). Structure having members:

long quot;

quotient

long rem;

remainder

Type for objects declared to store result of sizeof operator.

int abs(int n);

long labs(long n);

Returns absolute value of n.

(int num, int denom);

(long num, long denom);

Returns quotient and remainder of num/denom.

double atof(const char* s);

Equivalent to (s, (char**)) except that is not necessarily set on conversion error.

int atoi(const char* s);

Equivalent to (int)(s, (char**), 10) except that is not necessarily set on conversion error.

long atol(const char* s);

Equivalent to (s, (char**), 10) except that is not necessarily set on conversion error.

double (const char* s, char** endp);

Converts initial characters (ignoring leading white space) of s to type double. If endp non-null, stores pointer to unconverted suffix in *endp. On overflow, sets to and returns with the appropriate sign; on underflow, sets to and returns zero; otherwise returns converted value.

long (const char* s, char** endp, int base);

Converts initial characters (ignoring leading white space) of s to type long. If endp non-null, stores pointer to unconverted suffix in *endp. If base between 2 and 36, that base used for conversion; if zero, leading (after any sign) 0X or 0x implies hexadecimal, leading 0 (after any sign) implies octal, otherwise decimal assumed. Leading 0X or 0x permitted for base hexadecimal. On overflow, sets to and returns or (as appropriate for sign); otherwise returns converted value.

unsigned long (const char* s, char** endp, int base);

As for except result is unsigned long and value on overflow is .

void* calloc( nobj, size);

Returns pointer to zero-initialised newly-allocated space for an array of nobj objects each of size size, or on error.

void* malloc( size);

Returns pointer to uninitialised newly-allocated space for an object of size size, or on error.

void* realloc(void* p, size_t size);

Returns pointer to newly-allocated space for an object of size size, initialised, to minimum of old and new sizes, to existing contents of p (if non-null), or on error. On success, old object deallocated, otherwise unchanged.

void free(void* p);

If p non-null, deallocates space to which it points.

void ();

Terminates program abnormally, by calling ().

void (int status);

Terminates program normally. Functions installed using are called (in reverse order to that in which installed), open files are flushed, open streams are closed and control is returned to environment. status is returned to environment in implementation-dependent manner. Zero or indicates successful termination and indicates unsuccessful termination. Implementations may define other values.

int (void (*fcm)(void));

Registers fcn to be called when program terminates normally (or when main returns). Returns non-zero on failure.

int system(const char* s);

If s is not , passes s to environment for execution, and returns status reported by command processor; if s is , non-zero returned if environment has a command processor.

char* getenv(const char* name);

Returns string associated with name name from implementation's environment, or if no such string exists.

void* bsearch(const void* key, const void* base, n, size, int (*cmp)(const void* keyval, const void* datum));

Searches ordered array base (of n objects each of size size) for item matching key according to comparison function cmp. cmp must return negative value if first argument is less than second, zero if equal and positive if greater. Items of base are assumed to be in ascending order (according to cmp). Returns a pointer to an item matching key, or if none found.

void qsort(void* base, n, size, int (*cmp)(const void*, const void*));

Arranges into ascending order array base (of n objects each of size size) according to comparison function cmp. cmp must return negative value if first argument is less than second, zero if equal and positive if greater.

int (void);

Returns pseudo-random number in range 0 to .

void srand(unsigned int seed);

Uses seed as seed for new sequence of pseudo-random numbers. Initial seed is 1.

[]

Null pointer constant.

Type for objects declared to store result of sizeof operator.

char* strcpy(char* s, const char* ct);

Copies ct to s including terminating NUL and returns s.

char* strncpy(char* s, const char* ct, n);

Copies at most n characters of ct to s. Pads with NUL characters if ct is of length less than n. Note that this may leave s without NUL-termination. Return s.

char* strcat(char* s, const char* ct);

Concatenate ct to s and return s.

char* strncat(char* s, const char* ct, n);

Concatenate at most n characters of ct to s. NUL-terminates s and return it.

int strcmp(const char* cs, const char* ct);

Compares cs with ct, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

int strncmp(const char* cs, const char* ct, n);

Compares at most (the first) n characters of cs and ct, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

int strcoll(const char* cs, const char* ct);

Compares cs with ct according to locale, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

char* strchr(const char* cs, int c);

Returns pointer to first occurrence of c in cs, or if not found.

char* strrchr(const char* cs, int c);

Returns pointer to last occurrence of c in cs, or if not found.

strspn(const char* cs, const char* ct);

Returns length of prefix of cs which consists of characters which are in ct.

strcspn(const char* cs, const char* ct);

Returns length of prefix of cs which consists of characters which are not in ct.

char* strpbrk(const char* cs, const char* ct);

Returns pointer to first occurrence in cs of any character of ct, or if none is found.

char* strstr(const char* cs, const char* ct);

Returns pointer to first occurrence of ct within cs, or if none is found.

strlen(const char* cs);

Returns length of cs.

Returns pointer to implementation-defined message string corresponding with error n.

char* strtok(char* s, const char* t);

Searches s for next token delimited by any character from ct. Non- s indicates the first call of a sequence. If a token is found, it is NUL-terminated and returned, otherwise is returned. ct need not be identical for each call in a sequence.

strxfrm(char* s, const char* ct, n);

Stores in s no more than n characters (including terminating NUL) of a string produced from ct according to a locale-specific transformation. Returns length of entire transformed string.

void* (void* s, const void* ct, n);

Copies n characters from ct to s and returns s. s may be corrupted if objects overlap.

void* memmove(void* s, const void* ct, n);

Copies n characters from ct to s and returns s. s will not be corrupted if objects overlap.

int memcmp(const void* cs, const void* ct, n);

Compares at most (the first) n characters of cs and ct, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

void* memchr(const void* cs, int c, n);

Returns pointer to first occurrence of c in first n characters of cs, or if not found.

void* memset(void* s, int c, n);

Replaces each of the first n characters of s by c and returns s.

[]

CLOCKS_PER_SEC

The number of units per second.

Null pointer constant.

An arithmetic type elapsed processor representing time.

An arithmetic type representing calendar time.

Represents the components of calendar time:

int tm_sec;

seconds after the minute

int tm_min;

minutes after the hour

int tm_hour;

hours since midnight

int tm_mday;

day of the month

int tm_mon;

months since January

int tm_year;

years since 1900

int tm_wday;

days since Sunday

int tm_yday;

days since January 1

int tm_isdst;

Daylight Saving Time flag : is positive if DST is in effect, zero if not ineffect, negative if information not known.

Implementations may change field order and include additional fields.

clock(void);

Returns elapsed processor time used by program or -1 if not available.

time(* tp);

Returns current calendar time or -1 if not available. If tp is non-, return value is also assigned to *tp.

double difftime( time2, time1);

Returns the difference in seconds between time2 and time1.

mktime(* tp);

If necessary, adjusts fields of *tp to fall withing normal ranges. Returns the corresponding calendar time, or -1 if it cannot be represented.

char* (const * tp);

Returns the given time as a string of the form:
Sun Jan 3 13:08:42 1988\n\0

char* ctime(const * tp);

Returns string equivalent to calendar time tp converted to local time. Equivalent to:
((tp))

* gmtime(const * tp);

Returns calendar time *tp converted to Coordinated Universal Time, or if not available.

* (const * tp);

Returns calendar time *tp converted into localtime.

size_t strftime(char* s, size_t smax, const char* fmt, const * tp);

Formats *tp into s according to fmt. Places no more than smax characters into s, and returns number of characters produced (excluding terminating NUL), or 0 if greater than smax. Formatting conversions (%c) are:

A

name of weekday

a

abbreviated name of weekday

B

name of month

b

abbreviated name of month

c

local date and time representation

d

day of month [01-31]

H

hour (24-hour clock) [00-23]

I

hour (12-hour clock) [01-12]

j

day of year [001-366]

M

minute [00-59]

m

month [01-12]

p

local equivalent of "AM" or "PM"

S

second [00-61]

U

week number of year (Sunday as 1st day of week) [00-53]

W

week number of year (Monday as 1st day of week) [00-53]

w

weekday (Sunday as 0) [0-6]

X

local time representation

x

local date representation

Y

year with century

y

year without century [00-99]

Z

name (if any) of time zone

%

%

[]

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