1/* head.c - copy first lines from input to stdout.
2 *
3 * Copyright 2006 Timothy Elliott <tle@holymonkey.com>
4 *
5 * See http://opengroup.org/onlinepubs/9699919799/utilities/head.html
6
7USE_HEAD(NEWTOY(head, "?n#<0=10", TOYFLAG_USR|TOYFLAG_BIN))
8
9config HEAD
10  bool "head"
11  default y
12  help
13    usage: head [-n number] [file...]
14
15    Copy first lines from files to stdout. If no files listed, copy from
16    stdin. Filename "-" is a synonym for stdin.
17
18    -n	Number of lines to copy.
19*/
20
21#define FOR_head
22#include "toys.h"
23
24GLOBALS(
25  long lines;
26  int file_no;
27)
28
29static void do_head(int fd, char *name)
30{
31  int i, len, lines=TT.lines, size=sizeof(toybuf);
32
33  if (toys.optc > 1) {
34    // Print an extra newline for all but the first file
35    if (TT.file_no++) xprintf("\n");
36    xprintf("==> %s <==\n", name);
37    xflush();
38  }
39
40  while (lines) {
41    len = read(fd, toybuf, size);
42    if (len<0) perror_msg("%s",name);
43    if (len<1) break;
44
45    for(i=0; i<len;) if (toybuf[i++] == '\n' && !--lines) break;
46
47    xwrite(1, toybuf, i);
48  }
49}
50
51void head_main(void)
52{
53  char *arg = *toys.optargs;
54
55  // handle old "-42" style arguments
56  if (arg && *arg == '-' && arg[1]) {
57    TT.lines = atolx(arg+1);
58    toys.optc--;
59  } else arg = 0;
60  loopfiles(toys.optargs+!!arg, do_head);
61}
62