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tee.c
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tee.c
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#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include "tlpi_hdr.h"
#include "error_functions.c"
#ifndef BUF_SIZE /* Allow "cc -D" to override definition */
#define BUF_SIZE 1024
#endif
int main(int argc, char *argv[])
{
int inputFd, outputFd, openFlags, appendFlag;
mode_t filePerms;
ssize_t numRead;
char buf[BUF_SIZE], c;
if (argc < 2 || strcmp(argv[1], "--help") == 0)
usageErr("%s [-a] file\n", argv[0]);
while ((c = getopt(argc, argv, ":a")) != -1)
switch(c)
{
case 'a':
appendFlag = 1;
break;
default:
errExit("invalid flag %c", c);
}
openFlags = O_CREAT | O_WRONLY;
if (appendFlag == 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)
errExit("opening file %s %d", argv[optind], optind);
/* Transfer data until we encounter end of input or an error */
while ((numRead = read(STDIN_FILENO, buf, BUF_SIZE)) > 0)
{
if (write(outputFd, buf, numRead) != numRead)
fatal("couldn't write whole buffer to file");
if (write(STDOUT_FILENO, buf, numRead) != numRead)
fatal("couldn't write whole buffer to stdout");
}
if (close(outputFd) == -1)
errExit("close output");
exit(EXIT_SUCCESS);
}