C language——to Replace a specified Line in a Text File—V2

[root@localhost 桌面]# gedit tmp.c

// C Language to Replace a specified Line in a Text File

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

//filename: "/etc/hosts"
//str: "mpe.localhost"
//return the matched line number
int findline(char *filename, char *str)
{
    // open the file for reading
    FILE *file = fopen(filename, "r");

    // make sure the file opened properly
    if(NULL == file)
    {
        fprintf(stderr, "Cannot open file: %s\n", filename);
        return 1;
    }

    // set up the buffer to read the line into. Don't worry too much
    // if some of the lines are longer than 80 characters - the buffer
    // will be made bigger if need be.
    size_t buffer_size = 80;
    char *buffer = malloc(buffer_size * sizeof(char));

    // read each line and print it to the screen
    int line_number = 0, find = 0;
    while(-1 != getline(&buffer, &buffer_size, file))
    {
        line_number++;
        if(NULL != strstr(buffer, str))
        {
            find = 1;
            break;
        }
        //printf("%d: %s", line_number, buffer);
    }

    if(find == 0) line_number = 0;

    fclose(file);
    free(buffer);

    return line_number;
}

void replaceline(char *filename, int delete_line, char *newcontent)
{
    FILE *fileptr1, *fileptr2;
    //char filename[40];
    char c;
    int temp = 1;

    fileptr1 = fopen(filename, "r");
    //print the contents of file .
    while ((c = getc(fileptr1)) != EOF)
    {
        printf("%c", c);
    }

    //take fileptr1 to start point.
    rewind(fileptr1);
    //open tempinterm.txt in write mode
    fileptr2 = fopen("tempinterm.txt", "w");

    while ((c = getc(fileptr1)) != EOF)
    {
        //till the line to be deleted comes,copy the content to other
        if (temp != delete_line) {
            putc(c, fileptr2);
            while ((c = getc(fileptr1)) != '\n') putc(c, fileptr2);
            putc('\n', fileptr2);
            temp++;
        } else {
            while ((c = getc(fileptr1)) != '\n');    //read and skip the line
            //while ((c = getchar()) != '\n') putc(c, fileptr2);
            while(*newcontent != '\0') putc(*newcontent++, fileptr2);
            putc('\n', fileptr2);
            temp++;
        }
    }

    //append a new line at the end of file
    if(delete_line == 0)
    {
        while(*newcontent != '\0') putc(*newcontent++, fileptr2);
        putc('\n', fileptr2);
    }

    fclose(fileptr1);
    fclose(fileptr2);
    remove(filename);
    rename("tempinterm.txt", filename);
}

int main(void)
{
    FILE *fileptr1;
    char c;

    char filename[6] = "hosts";

    int line = findline(filename, "mpe.localhost");
    replaceline(filename, line, "10.108.162.227   mpe.localhost");

    fileptr1 = fopen(filename, "r");
    //reads the character from file
    //until last character of file is encountered
    while ((c = getc(fileptr1)) != EOF) printf("%c", c);
    fclose(fileptr1);
    return 0;
}

[root@localhost 桌面]# gcc tmp.c -o tmp
[root@localhost 桌面]# ./tmp
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
10.108.162.227   mpe.localhost
[root@localhost 桌面]#