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1 /* vi: set sw=4 ts=4:
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2 *
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3 * head.c - copy first lines from input to stdout.
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4 *
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5 * Copyright 2006 Timothy Elliott <tle@holymonkey.com>
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6 *
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7 * See http://www.opengroup.org/onlinepubs/009695399/utilities/head.html
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8
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9 USE_HEAD(NEWTOY(head, "n#<0=10", TOYFLAG_BIN))
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444
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10
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11 config HEAD
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12 bool "head"
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13 default y
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14 help
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15 usage: head [-n number] [file...]
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16
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17 Copy first lines from files to stdout. If no files listed, copy from
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18 stdin. Filename "-" is a synonym for stdin.
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19
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20 -n Number of lines to copy.
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21 */
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22
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23 #include "toys.h"
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24
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25 DEFINE_GLOBALS(
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26 long lines;
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27 int file_no;
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28 )
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29
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30 #define TT this.head
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31
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32 static void do_head(int fd, char *name)
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33 {
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34 int i, len, lines=TT.lines, size=sizeof(toybuf);
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35
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36 if (toys.optc > 1) {
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37 // Print an extra newline for all but the first file
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451
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38 if (TT.file_no++) xprintf("\n");
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39 xprintf("==> %s <==\n", name);
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451
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40 xflush();
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41 }
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42
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43 while (lines) {
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44 len = read(fd, toybuf, size);
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45 if (len<0) {
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46 perror_msg("%s",name);
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47 toys.exitval = EXIT_FAILURE;
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48 }
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49 if (len<1) break;
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50
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51 for(i=0; i<len;)
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52 if (toybuf[i++] == '\n' && !--lines) break;
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53
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54 xwrite(1, toybuf, i);
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444
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55 }
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56 }
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57
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58 void head_main(void)
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59 {
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60 loopfiles(toys.optargs, do_head);
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61 }
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