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

[root@localhost 桌面]# gedit tmp.c

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

#include <stdio.h>

int main(void)
{
    FILE *fileptr1, *fileptr2;
    char filechar[40];
    char c;
    int delete_line, temp = 1;

    printf("Enter file name: ");
    scanf("%s", filechar);

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

    printf("\nEnter line number to be deleted and replaced: ");
    scanf("%d", &delete_line);

    //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 ask for new text
            printf("Enter new text: ");

            //flush the input stream
            fflush(stdin);
            getchar();    //delete blank line

            while ((c = getchar()) != '\n') putc(c, fileptr2);
            //take the data from user and place it in new file
            putc('\n', fileptr2);
            temp++;
        }
    }

    fclose(fileptr1);
    fclose(fileptr2);
    remove(filechar);
    rename("tempinterm.txt", filechar);
    fileptr1 = fopen(filechar, "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
Enter file name: hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

Enter line number to be deleted and replaced: 1
Enter new text: asdf
asdf
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
[root@localhost 桌面]#