Print the contents of a file to stdout.

gistfile1.c

#include <stdio.h>
#include <errno.h>

int main(int argc, char **argv)
{
    if (argc == 1) return 0;
    if (argc == 2) {
        char *filename = argv[1];
        FILE *fp = fopen(filename, "r");
        if (!fp) {
            perror(NULL);
            return errno;
        }
        char buf[11];
        int read;
        while ((read = fread(buf, sizeof(char), 10, fp)) != 0) {
            buf[read] = '\0';
            printf(buf);
        }
        if (fp && fclose(fp) == EOF) {
            perror(NULL);
            return errno;
        }
    }
    return 0;
}

Oh, and printf interprets that first arg as a format string, so if the file contains something like %d, you are in funland. Either use fputs or printf("%s", buf).

(Note that puts appends a newline after each call, unlike fputs, just to throw you. So puts(str) is actually basically fputs(str, stdout); putchar('\n');.)

Also: Once you have file reading, you can actually copy stdin to stdout by telling it to read from /dev/fd/0 or /dev/stdin. Fake device files are fun! :)