gistfile1.c

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "tlpi_hdr.h"

#ifndef BUF_SIZE
#define BUF_SIZE 1024
#endif

extern int optind, optopt;
extern char *optarg;

#define printable(ch) (isprint((unsigned char) ch) ? ch : '#')

static void
usageError(char *progName, char *msg, int opt)
{
        if (msg != NULL && opt != 0)
                fprintf(stderr, "%s (-%c)\n", msg, printable(opt));
        fprintf(stderr, "Usage: %s [-a] file\n", progName);
}


int
main(int argc, char *argv[])
{
        int opt, fd, numRead, teeFd;
        char buf[BUF_SIZE];
        char *appendFile;

        appendFile = NULL;


        while ((opt = getopt(argc, argv, "+:a")) != -1) {
                switch (opt) {
                case 'a': appendFile = optarg; break;
                case '?': usageError(argv[0], "Unrecognized option", optopt);
                }
        }
        if (optind > argc) {
                fprintf(stderr, "File not specified\n");
                exit(EXIT_FAILURE);
        }

        if (appendFile != NULL) {
                teeFd = open(appendFile, O_RDWR | O_CREAT |
                        O_TRUNC, S_IRUSR | S_IWUSR);
        } else {
                teeFd = open(argv[optind], O_RDWR | O_CREAT |
                        O_APPEND, S_IRUSR | S_IWUSR);
        }

        while ((numRead = read(STDIN_FILENO, buf, BUF_SIZE)) > 0)  {
                if (write(STDOUT_FILENO, buf, numRead) != numRead)

                if (write(STDOUT_FILENO, buf, numRead) != numRead)
                        fatal("Couldnt write whole buffer");
                if (write(teeFd, buf, numRead) != numRead)
                        fatal("Couldnt write whole buffer");
                fflush(stdout);
        }

        exit(EXIT_SUCCESS);
}