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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_raw(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