view toys/head.c @ 543:60b97ba66a70

Extensive semi-gratuitous refactoring: factor out common code, handle euid!=uid and egid!=gid cases. (Note: test suite requires root access, possibly container support.)
author Rob Landley <>
date Mon, 12 Mar 2012 23:00:28 -0500
parents f4cc0a2aa440
line wrap: on
line source

/* vi: set sw=4 ts=4:
 * head.c - copy first lines from input to stdout.
 * Copyright 2006 Timothy Elliott <>
 * See

USE_HEAD(NEWTOY(head, "n#<0=10", TOYFLAG_BIN))

config HEAD
	bool "head"
	default y
	  usage: head [-n number] [file...]

	  Copy first lines from files to stdout. If no files listed, copy from
	  stdin. Filename "-" is a synonym for stdin.

	  -n	Number of lines to copy.

#include "toys.h"

	long lines;
	int file_no;

#define TT this.head

static void do_head(int fd, char *name)
	int i, len, lines=TT.lines, size=sizeof(toybuf);

	if (toys.optc > 1) {
		// Print an extra newline for all but the first file
		if (TT.file_no++) xprintf("\n");
		xprintf("==> %s <==\n", name);

	while (lines) {
		len = read(fd, toybuf, size);
		if (len<0) {
			toys.exitval = EXIT_FAILURE;
		if (len<1) break;
		for(i=0; i<len;)
			if (toybuf[i++] == '\n' && !--lines) break;

		xwrite(1, toybuf, i);

void head_main(void)
	loopfiles(toys.optargs, do_head);