/* $OpenBSD: head.c,v 1.16 2013/11/26 13:21:17 deraadt Exp $ */ /* * Copyright (c) 1980, 1987 Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <limits.h> #include <err.h> #include <errno.h> #include <unistd.h> static void usage(void); /* * head - give the first few lines of a stream or of each of a set of files * * Bill Joy UCB August 24, 1977 */ int main(int argc, char *argv[]) { long cnt; int ch, firsttime; long linecnt = 10; char *p = NULL; /* handle obsolete -number syntax */ if (argc > 1 && argv[1][0] == '-' && isdigit((unsigned char)argv[1][1])) { p = argv[1] + 1; argc--; argv++; } while ((ch = getopt(argc, argv, "n:")) != -1) { switch (ch) { case 'n': p = optarg; break; default: usage(); } } argc -= optind, argv += optind; if (p) { const char *errstr; linecnt = strtonum(p, 1, LONG_MAX, &errstr); if (errstr) errx(1, "line count %s: %s", errstr, p); } /* setlinebuf(stdout); */ for (firsttime = 1; ; firsttime = 0) { if (!*argv) { if (!firsttime) exit(0); } else { if (!freopen(*argv, "r", stdin)) { warn("%s", *argv++); continue; } if (argc > 1) { if (!firsttime) putchar('\n'); printf("==> %s <==\n", *argv); } ++argv; } for (cnt = linecnt; cnt && !feof(stdin); --cnt) while ((ch = getchar()) != EOF) if (putchar(ch) == '\n') break; } /*NOTREACHED*/ } static void usage(void) { fputs("usage: head [-count | -n count] [file ...]\n", stderr); exit(1); }