examples/loadables/head.c

/* head - copy first part of files. */

/* See Makefile for compilation details. */

/*
   Copyright (C) 1999-2009 Free Software Foundation, Inc.

   This file is part of GNU Bash.
   Bash is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   Bash is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with Bash.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "config.h"

#include "bashtypes.h"
#include "posixstat.h"
#include "filecntl.h"

#if defined (HAVE_UNISTD_H)
#  include <unistd.h>
#endif

#include "bashansi.h"

#include <stdio.h>
#include <errno.h>
#include "chartypes.h"

#include "builtins.h"
#include "shell.h"
#include "bashgetopt.h"
#include "common.h"

#if !defined (errno)
#include <errno.h>
#endif

static void
munge_list (list)
     WORD_LIST *list;
{
  WORD_LIST *l, *nl;
  WORD_DESC *wd;
  char *arg;

  for (l = list; l; l = l->next)
    {
      arg = l->word->word;
      if (arg[0] != '-' || arg[1] == '-' || (DIGIT(arg[1]) == 0))
        return;
      /* We have -[0-9]* */
      wd = make_bare_word (arg+1);
      nl = make_word_list (wd, l->next);
      l->word->word[1] = 'n';
      l->word->word[2] = '\0';
      l->next = nl;
      l = nl;	/* skip over new argument */
    }
}

static int
file_head (fp, cnt)
     FILE *fp;
     int cnt;
{
  int ch;

  while (cnt--)
    {
      while ((ch = getc (fp)) != EOF)
	{
	  if (putchar (ch) == EOF)
	    {
	      builtin_error ("write error: %s", strerror (errno));
	      return EXECUTION_FAILURE;
	    }
	  if (ch == '\n')
	    break;
	}
    }
}

head_builtin (list)
     WORD_LIST *list;
{
  int nline, opt, rval;
  WORD_LIST *l;
  FILE *fp;

  char *t;

  munge_list (list);	/* change -num into -n num */

  reset_internal_getopt ();
  nline = 10;
  while ((opt = internal_getopt (list, "n:")) != -1)
    {
      switch (opt)
	{
	case 'n':
	  nline = atoi (list_optarg);
	  if (nline <= 0)
	    {
	      builtin_error ("bad line count: %s", list_optarg);
	      return (EX_USAGE);
	    }
	  break;
	default:
	  builtin_usage ();
	  return (EX_USAGE);
	}
    }
  list = loptend;

  if (list == 0)
    return (file_head (stdin, nline));

  for (rval = EXECUTION_SUCCESS, opt = 1, l = list; l; l = l->next)
    {
      fp = fopen (l->word->word, "r");
      if (fp == NULL)
	{
	  builtin_error ("%s: %s", l->word->word, strerror (errno));
	  continue;
	}
      if (list->next)	/* more than one file */
	{
	  printf ("%s==> %s <==\n", opt ? "" : "\n", l->word->word);
	  opt = 0;
	}
      rval = file_head (fp, nline);
      fclose (fp);
    }
   
  return (rval);
}

char *head_doc[] = {
	"Display lines from beginning of file.",
	"",
	"Copy the first N lines from the input files to the standard output.",
	"N is supplied as an argument to the `-n' option.  If N is not given,",
	"the first ten lines are copied.",
	(char *)NULL
};

struct builtin head_struct = {
	"head",			/* builtin name */
	head_builtin,		/* function implementing the builtin */
	BUILTIN_ENABLED,	/* initial flags for builtin */
	head_doc,		/* array of long documentation strings. */
	"head [-n num] [file ...]", /* usage synopsis; becomes short_doc */
	0			/* reserved for internal use */
};