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
7 USE_HEAD(NEWTOY(head, "?n#<0=10", TOYFLAG_USR|TOYFLAG_BIN))
8
9 config 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
GLOBALS(long lines;int file_no;)24 GLOBALS(
25 long lines;
26 int file_no;
27 )
28
29 static 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
head_main(void)51 void 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