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dated.c
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dated.c
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#include <sys/time.h>
#include <sys/select.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <time.h>
#include <err.h>
#include <getopt.h>
#include <fcntl.h>
static const char usage[] =
"usage: ... | dated [-f format]\n";
int
main(int argc, char **argv)
{
int c;
char *format = "%x %X ";
fd_set fds;
int flags;
time_t now;
struct tm *now_tm;
char now_str[512];
char buf[4096];
ssize_t nread, i;
int newline = 1;
#if defined(__OpenBSD)
pledge("stdio", NULL);
#endif
while ((c = getopt(argc, argv, "f:")) != -1) {
switch (c) {
case 'f':
format = optarg;
break;
default:
fputs(usage, stderr);
return 1;
}
}
if (argc > optind) {
fputs(usage, stderr);
return 1;
}
FD_ZERO(&fds);
/*
* We want to take the time the moment data is put on stdin, not when
* we happen to output it. To this, we use select() to wait for data,
* taking the time once, then processing all available data. To know
* what "all available", we make the stream nonblocking.
*/
if ((flags = fcntl(STDIN_FILENO, F_GETFL)) == -1)
err(1, "F_GETFL");
if (fcntl(STDIN_FILENO, F_SETFL, flags | O_NONBLOCK) == -1)
err(1, "F_SETFL");
while (1) {
FD_SET(STDIN_FILENO, &fds);
if (select(STDIN_FILENO+1, &fds, NULL, NULL, NULL) == -1)
err(1, "select");
if ((now = time(NULL)) == (time_t)-1)
err(1, "time");
if (!(now_tm = localtime(&now)))
err(1, "localtime");
if (!strftime(now_str, sizeof(now_str), format, now_tm))
err(1, "strftime");
while ((nread = read(STDIN_FILENO, buf, sizeof(buf))) != -1) {
if (!nread)
return 0;
for (i = 0; i < nread; i++) {
if (newline)
fputs(now_str, stdout);
putchar(buf[i]);
newline = buf[i] == '\n';
}
}
if (errno != EAGAIN)
err(1, NULL);
}
}