sbase/head.c
FRIGN 9144d51594 Check getline()-return-values properly
It's not useful when 0 is returned anyway, so be sure that we have a
string with length > 0, this also solves some indexing-gotchas like
"len - 1" and so on.
Also, add checked getline()'s whenever it has been forgotten and
clean up the error-messages.
2015-03-27 14:49:48 +01:00

71 lines
1.1 KiB
C

/* See LICENSE file for copyright and license details. */
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include "util.h"
static void
head(FILE *fp, const char *fname, size_t n)
{
char *buf = NULL;
size_t i = 0, size = 0;
ssize_t len;
while (i < n && (len = getline(&buf, &size, fp)) > 0) {
fputs(buf, stdout);
i += (len && (buf[len - 1] == '\n'));
}
free(buf);
if (ferror(fp))
eprintf("getline %s:", fname);
}
static void
usage(void)
{
eprintf("usage: %s [-num | -n num] [file ...]\n", argv0);
}
int
main(int argc, char *argv[])
{
size_t n = 10;
FILE *fp;
int ret = 0, newline, many;
ARGBEGIN {
case 'n':
n = estrtonum(EARGF(usage()), 0, MIN(LLONG_MAX, SIZE_MAX));
break;
ARGNUM:
n = ARGNUMF();
break;
default:
usage();
} ARGEND;
if (!argc) {
head(stdin, "<stdin>", n);
} else {
many = argc > 1;
for (newline = 0; *argv; argc--, argv++) {
if (!(fp = fopen(*argv, "r"))) {
weprintf("fopen %s:", *argv);
ret = 1;
continue;
}
if (many) {
if (newline)
putchar('\n');
printf("==> %s <==\n", *argv);
}
newline = 1;
head(fp, *argv, n);
fclose(fp);
}
}
return ret;
}