I implemented the tee command from linux. The program implements the -a option
Reads standard input until end-of-file, write a copy of the input to standard output and to the file named in argv[1].
This is another implementation of the tee command. I posted another code trying to implement the command, but I think I found a better implementation.
Please criticize the implementation
code:
#define _GNU_SOURCE
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#ifndef BUF_SIZE
#define BUF_SIZE 1024
#endif
static void usage(int exit_code) {
printf("Usage: mytee [-a] FILE\n");
exit(exit_code);
}
int main(int argc, char *argv[]) {
int outputFd, openFlags;
mode_t filePerms;
int aflag = 0;
char buf[BUF_SIZE + 1];
ssize_t numRead;
int c;
while ((c = getopt(argc, argv, "ha")) != -1) {
switch (c) {
case 'h': usage(0); break;
case 'a': aflag = 1; break;
}
}
if (optind >= argc) {
usage(1);
}
openFlags = O_CREAT | O_WRONLY;
if (aflag == 1) {
openFlags |= O_APPEND;
} else {
openFlags |= O_TRUNC;
}
filePerms = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP |
S_IROTH | S_IWOTH; /* rw-rw-rw- */
outputFd = open(argv[optind], openFlags, filePerms);
if (outputFd == -1) {
perror("open");
exit(1);
}
while ((numRead = read(STDIN_FILENO, buf, BUF_SIZE)) > 0) {
buf[numRead] = '\0';
// write to stdout
printf("%s", buf);
// write to output file (only up to numRead!)
if (write(outputFd, buf, numRead) != numRead) {
perror("write");
exit(1);
}
}
if (numRead == -1) {
perror("read");
exit(1);
}
if (close(outputFd) == -1) {
perror("close output file");
exit(1);
}
exit(0);
}
