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annotate toys/posix/head.c @ 1776:7bf68329eb3b draft default tip

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Repository switched to git at https://github.com/landley/toybox
author Rob Landley <rob@landley.net>
date Thu, 09 Apr 2015 02:28:32 -0500
parents 57f2a26fa92c
children
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1 /* head.c - copy first lines from input to stdout.
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2 *
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3 * Copyright 2006 Timothy Elliott <tle@holymonkey.com>
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4 *
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5 * See http://opengroup.org/onlinepubs/9699919799/utilities/head.html
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6
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7 USE_HEAD(NEWTOY(head, "?n#<0=10", TOYFLAG_USR|TOYFLAG_BIN))
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8
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9 config HEAD
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10 bool "head"
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11 default y
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12 help
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13 usage: head [-n number] [file...]
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15 Copy first lines from files to stdout. If no files listed, copy from
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16 stdin. Filename "-" is a synonym for stdin.
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18 -n Number of lines to copy.
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19 */
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20
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21 #define FOR_head
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22 #include "toys.h"
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23
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24 GLOBALS(
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25 long lines;
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26 int file_no;
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27 )
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28
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29 static void do_head(int fd, char *name)
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30 {
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31 int i, len, lines=TT.lines, size=sizeof(toybuf);
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32
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33 if (toys.optc > 1) {
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34 // Print an extra newline for all but the first file
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35 if (TT.file_no++) xprintf("\n");
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36 xprintf("==> %s <==\n", name);
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37 xflush();
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38 }
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40 while (lines) {
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41 len = read(fd, toybuf, size);
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42 if (len<0) perror_msg("%s",name);
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43 if (len<1) break;
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45 for(i=0; i<len;) if (toybuf[i++] == '\n' && !--lines) break;
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47 xwrite(1, toybuf, i);
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48 }
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49 }
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51 void head_main(void)
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52 {
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53 char *arg = *toys.optargs;
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54
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55 // handle old "-42" style arguments
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56 if (arg && *arg == '-' && arg[1]) {
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57 TT.lines = atolx(arg+1);
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58 toys.optc--;
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59 } else arg = 0;
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60 loopfiles(toys.optargs+!!arg, do_head);
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61 }