sbase/head.c

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