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/* head.c - copy first lines from input to stdout.
*
* Copyright 2006 Timothy Elliott <tle@holymonkey.com>
*
* See http://opengroup.org/onlinepubs/9699919799/utilities/head.html
*
* Deviations from posix: -c
USE_HEAD(NEWTOY(head, "?n(lines)#<0=10c(bytes)#<0qv[-nc]", TOYFLAG_USR|TOYFLAG_BIN))
config HEAD
bool "head"
default y
help
usage: head [-n number] [file...]
Copy first lines from files to stdout. If no files listed, copy from
stdin. Filename "-" is a synonym for stdin.
-n Number of lines to copy
-c Number of bytes to copy
-q Never print headers
-v Always print headers
*/
#define FOR_head
#include "toys.h"
GLOBALS(
long c, n;
int file_no;
)
static void do_head(int fd, char *name)
{
int i, len, lines=TT.n, bytes=TT.c;
if ((toys.optc > 1 && !(toys.optflags & FLAG_q)) || toys.optflags & FLAG_v) {
// Print an extra newline for all but the first file
if (TT.file_no) xprintf("\n");
xprintf("==> %s <==\n", name);
}
while ((toys.optflags&FLAG_c) ? bytes : lines) {
len = read(fd, toybuf, sizeof(toybuf));
if (len<0) perror_msg_raw(name);
if (len<1) break;
if (bytes) {
i = bytes >= len ? len : bytes;
bytes -= i;
} else for(i=0; i<len;) if (toybuf[i++] == '\n' && !--lines) break;
xwrite(1, toybuf, i);
}
TT.file_no++;
}
void head_main(void)
{
char *arg = *toys.optargs;
// handle old "-42" style arguments
if (arg && *arg == '-' && arg[1]) {
TT.n = atolx(arg+1);
toys.optc--;
} else arg = 0;
loopfiles(toys.optargs+!!arg, do_head);
}
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