toaruos/apps/head.c

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2018-10-02 16:36:44 +03:00
/* vim: tabstop=4 shiftwidth=4 noexpandtab
* This file is part of ToaruOS and is released under the terms
* of the NCSA / University of Illinois License - see LICENSE.md
* Copyright (C) 2018 K. Lange
*
* head - Print the first `n` lines of a file.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <getopt.h>
#include <errno.h>
int main(int argc, char * argv[]) {
int n = 10;
int opt;
int print_names = 0;
int retval = 0;
while ((opt = getopt(argc, argv, "n:")) != -1) {
switch (opt) {
case 'n':
n = atoi(optarg);
break;
}
}
if (argc > optind + 1) {
/* Multiple files */
print_names = 1;
}
if (argc == optind) {
/* This is silly, but should work due to reasons. */
argv[optind] = "-";
argc++;
}
for (int i = optind; i < argc; ++i) {
FILE * f = (!strcmp(argv[i],"-")) ? stdin : fopen(argv[i],"r");
if (!f) {
fprintf(stderr, "%s: %s: %s\n", argv[0], argv[i], strerror(errno));
retval = 1;
continue;
}
if (print_names) {
fprintf(stdout, "==> %s <==\n", (f == stdin) ? "standard input" : argv[i]);
}
int line = 1;
while (!feof(f)) {
int c = fgetc(f);
if (c >= 0) {
fputc(c, stdout);
if (c == '\n') {
line++;
if (line > n) break;
}
}
}
if (f != stdin) {
fclose(f);
}
}
return retval;
}