Programming

char buf[4096];
FILE *fpold=fopen("filename", "r");
FILE *fpnew=fopen("newfile", "w+");

while(fgets(buf, 4096, fp) != NULL) // Read all lines from filename one-by-one
{
        int val;
        char *last=(buf+strlen(buf))-1; // Point to last character

        while(isspace(*last)) last--; // Loop backwards across the ending newline
        while(isdigit(*last)) last--; // Loop backwards across digits
        // 'last' now points to the first non-digit before the number.
        last[0]='\0'; // Change it into a NULL.
        last++; // Point to the character after, i.e. the number itself.

        // 'buf' now points to the string and only the string,
        // and 'last' points to the number and only the number.

        sscanf("%d", &val); // convert string into integer

        ////////
        // To alter the contents of the file, alter 'buf' or 'val' here.
        ////////

        fprintf(fpnew, "%s %d\n", buf, val); // Write all contents back into 'fpnew'.
}

fclose(fpold);

// Now, if you really want to, you can re-open fpold as write, read lines one-by-one from fpnew, and write them back into fpold.
rewind(fpnew);
...

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

typedef char buffer[128];


char * chomp(char * line)
{
    char **p = &line;
    strsep(p, "\r\n");
    return line;
}

int main( int argc, char **argv )
{
    buffer      in, out;
    int number;

    while ( fgets(in, sizeof in, stdin) ) {
        chomp(in);
        sscanf(in, "%s %d\n", out, &number); 
        printf("%s = %s %d\n", in, out, number);
    }

    return 0;
}