/***********************************************************************

*                                                                      *

*               This software is part of the ast package               *

*          Copyright (c) 1992-2012 AT&T Intellectual Property          *

*                      and is licensed under the                       *

*                 Eclipse Public License, Version 1.0                  *

*                    by AT&T Intellectual Property                     *

*                                                                      *

*                A copy of the License is available at                 *

*          http://www.eclipse.org/org/documents/epl-v10.html           *

*         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *

*                                                                      *

*              Information and Software Systems Research               *

*                            AT&T Research                             *

*                           Florham Park NJ                            *

*                                                                      *

*                 Glenn Fowler <gsf@research.att.com>                  *

*                  David Korn <dgk@research.att.com>                   *

*                                                                      *

***********************************************************************/

#pragma prototyped

/*

 * David Korn

 * AT&T Bell Laboratories

 *

 * output the beginning portion of one or more files

 */

static const char usage[] =

"[-n?\n@(#)$Id: head (AT&T Research) 2012-05-31 $\n]"

USAGE_LICENSE

"[+NAME?head - output beginning portion of one or more files ]"

"[+DESCRIPTION?\bhead\b copies one or more input files to standard "

    "output stopping at a designated point for each file or to the end of "

    "the file whichever comes first. Copying ends at the point indicated by "

    "the options. By default a header of the form \b==> \b\afilename\a\b "

    "<==\b is output before all but the first file but this can be changed "

    "with the \b-q\b and \b-v\b options.]"

"[+?If no \afile\a is given, or if the \afile\a is \b-\b, \bhead\b "

    "copies from standard input starting at the current location.]"

"[+?The option argument for \b-c\b, and \b-s\b can optionally be "

    "followed by one of the following characters to specify a different unit "

    "other than a single byte:]"

    "{"

        "[+b?512 bytes.]"

        "[+k?1-killobyte.]"

        "[+m?1-megabyte.]"

    "}"

"[+?For backwards compatibility, \b-\b\anumber\a is equivalent to \b-n\b "

    "\anumber\a.]"

"[n:lines?Copy \alines\a lines from each file.]#[lines:=10]"

"[c:bytes?Copy \achars\a bytes from each file.]#[chars]"

"[q:quiet|silent?Never ouput filename headers.]"

"[s:skip?Skip \askip\a characters or lines from each file before "

    "copying.]#[skip]"

"[v:verbose?Always ouput filename headers.]"

    "\n\n"

"[ file ... ]"

    "\n\n"

"[+EXIT STATUS?]"

    "{"

        "[+0?All files copied successfully.]"

        "[+>0?One or more files did not copy.]"

    "}"

"[+SEE ALSO?\bcat\b(1), \btail\b(1)]"

;

#include <cmd.h>

int

b_head(int argc, register char** argv, Shbltin_t* context)

{

	static const char	header_fmt[] = "\n==> %s <==\n";

	register Sfio_t*	fp;

	register char*		cp;

	register off_t		keep = 10;

	register off_t		skip = 0;

	register int		delim = '\n';

	int			header = 1;

	char*			format = (char*)header_fmt+1;

	cmdinit(argc, argv, context, ERROR_CATALOG, 0);

	for (;;)

	{

		switch (optget(argv, usage))

		{

		case 'c':

			delim = -1;

			/*FALLTHROUGH*/

		case 'n':

			if (opt_info.offset && argv[opt_info.index][opt_info.offset] == 'c')

			{

				delim = -1;

				opt_info.offset++;

			}

			if ((keep = opt_info.number) <=0)

				error(2, "%s: %I*d: positive numeric option argument expected", opt_info.name, sizeof(keep), keep);

			continue;

		case 'q':

			header = argc;

			continue;

		case 'v':

			header = 0;

			continue;

		case 's':

			skip = opt_info.number;

			continue;

		case '?':

			error(ERROR_usage(2), "%s", opt_info.arg);

			continue;

		case ':':

			error(2, "%s", opt_info.arg);

			continue;

		}

		break;

	}

	argv += opt_info.index;

	argc -= opt_info.index;

	if (error_info.errors)

		error(ERROR_usage(2), "%s", optusage(NiL));

	if (cp = *argv)

		argv++;

	do

	{

		if (!cp || streq(cp, "-"))

		{

			cp = "/dev/stdin";

			fp = sfstdin;

			sfset(fp, SF_SHARE, 1);

		}

		else if (!(fp = sfopen(NiL, cp, "r")))

		{

			error(ERROR_system(0), "%s: cannot open", cp);

			continue;

		}

		if (argc > header)

			sfprintf(sfstdout, format, cp);

		format = (char*)header_fmt;

		if (skip > 0)

			sfmove(fp, NiL, skip, delim);

		if (sfmove(fp, sfstdout, keep, delim) < 0 && !ERROR_PIPE(errno) && errno != EINTR)

			error(ERROR_system(0), "%s: read error", cp);

		if (fp != sfstdin)

			sfclose(fp);

	} while (cp = *argv++);

	if (sfsync(sfstdout))

		error(ERROR_system(0), "write error");

	return error_info.errors != 0;

}