1/* head - copy first part of files. */
2
3/* See Makefile for compilation details. */
4
5#include "config.h"
6
7#include "bashtypes.h"
8#include "posixstat.h"
9#include "filecntl.h"
10
11#if defined (HAVE_UNISTD_H)
12#  include <unistd.h>
13#endif
14
15#include "bashansi.h"
16
17#include <stdio.h>
18#include <errno.h>
19#include "chartypes.h"
20
21#include "builtins.h"
22#include "shell.h"
23#include "bashgetopt.h"
24
25#if !defined (errno)
26extern int errno;
27#endif
28
29static void
30munge_list (list)
31     WORD_LIST *list;
32{
33  WORD_LIST *l, *nl;
34  WORD_DESC *wd;
35  char *arg;
36
37  for (l = list; l; l = l->next)
38    {
39      arg = l->word->word;
40      if (arg[0] != '-' || arg[1] == '-' || (DIGIT(arg[1]) == 0))
41        return;
42      /* We have -[0-9]* */
43      wd = make_bare_word (arg+1);
44      nl = make_word_list (wd, l->next);
45      l->word->word[1] = 'n';
46      l->word->word[2] = '\0';
47      l->next = nl;
48      l = nl;	/* skip over new argument */
49    }
50}
51
52static int
53file_head (fp, cnt)
54     FILE *fp;
55     int cnt;
56{
57  int ch;
58
59  while (cnt--)
60    {
61      while ((ch = getc (fp)) != EOF)
62	{
63	  if (putchar (ch) == EOF)
64	    {
65	      builtin_error ("write error: %s", strerror (errno));
66	      return EXECUTION_FAILURE;
67	    }
68	  if (ch == '\n')
69	    break;
70	}
71    }
72}
73
74head_builtin (list)
75     WORD_LIST *list;
76{
77  int nline, opt, rval;
78  WORD_LIST *l;
79  FILE *fp;
80
81  char *t;
82
83  munge_list (list);	/* change -num into -n num */
84
85  reset_internal_getopt ();
86  nline = 10;
87  while ((opt = internal_getopt (list, "n:")) != -1)
88    {
89      switch (opt)
90	{
91	case 'n':
92	  nline = atoi (list_optarg);
93	  if (nline <= 0)
94	    {
95	      builtin_error ("bad line count: %s", list_optarg);
96	      return (EX_USAGE);
97	    }
98	  break;
99	default:
100	  builtin_usage ();
101	  return (EX_USAGE);
102	}
103    }
104  list = loptend;
105
106  if (list == 0)
107    return (file_head (stdin, nline));
108
109  for (rval = EXECUTION_SUCCESS, opt = 1, l = list; l; l = l->next)
110    {
111      fp = fopen (l->word->word, "r");
112      if (fp == NULL)
113	{
114	  builtin_error ("%s: %s", l->word->word, strerror (errno));
115	  continue;
116	}
117      if (list->next)	/* more than one file */
118	{
119	  printf ("%s==> %s <==\n", opt ? "" : "\n", l->word->word);
120	  opt = 0;
121	}
122      rval = file_head (fp, nline);
123      fclose (fp);
124    }
125
126  return (rval);
127}
128
129char *head_doc[] = {
130	"Copy the first N lines from the input files to the standard output.",
131	"N is supplied as an argument to the `-n' option.  If N is not given,",
132	"the first ten lines are copied.",
133	(char *)NULL
134};
135
136struct builtin head_struct = {
137	"head",			/* builtin name */
138	head_builtin,		/* function implementing the builtin */
139	BUILTIN_ENABLED,	/* initial flags for builtin */
140	head_doc,		/* array of long documentation strings. */
141	"head [-n num] [file ...]", /* usage synopsis; becomes short_doc */
142	0			/* reserved for internal use */
143};
144