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 * Deviations from posix: -c
8
9 USE_HEAD(NEWTOY(head, "?n#<0=10c#<0qv[-nc]", TOYFLAG_USR|TOYFLAG_BIN))
10
11 config HEAD
12 bool "head"
13 default y
14 help
15 usage: head [-n number] [file...]
16
17 Copy first lines from files to stdout. If no files listed, copy from
18 stdin. Filename "-" is a synonym for stdin.
19
20 -n Number of lines to copy
21 -c Number of bytes to copy
22 -q Never print headers
23 -v Always print headers
24 */
25
26 #define FOR_head
27 #include "toys.h"
28
GLOBALS(long bytes;long lines;int file_no;)29 GLOBALS(
30 long bytes;
31 long lines;
32 int file_no;
33 )
34
35 static void do_head(int fd, char *name)
36 {
37 int i, len, lines=TT.lines, bytes=TT.bytes;
38
39 if ((toys.optc > 1 && !(toys.optflags & FLAG_q)) || toys.optflags & FLAG_v) {
40 // Print an extra newline for all but the first file
41 if (TT.file_no) xprintf("\n");
42 xprintf("==> %s <==\n", name);
43 xflush();
44 }
45
46 while ((toys.optflags&FLAG_c) ? bytes : lines) {
47 len = read(fd, toybuf, sizeof(toybuf));
48 if (len<0) perror_msg_raw(name);
49 if (len<1) break;
50
51 if (bytes) {
52 i = bytes >= len ? len : bytes;
53 bytes -= i;
54 } else for(i=0; i<len;) if (toybuf[i++] == '\n' && !--lines) break;
55
56 xwrite(1, toybuf, i);
57 }
58
59 TT.file_no++;
60 }
61
head_main(void)62 void head_main(void)
63 {
64 char *arg = *toys.optargs;
65
66 // handle old "-42" style arguments
67 if (arg && *arg == '-' && arg[1]) {
68 TT.lines = atolx(arg+1);
69 toys.optc--;
70 } else arg = 0;
71 loopfiles(toys.optargs+!!arg, do_head);
72 }
73