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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
USE_HEAD(NEWTOY(head, "?n#<0=10", 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.
*/
#define FOR_head
#include "toys.h"
GLOBALS(
long lines;
int file_no;
)
static void do_head(int fd, char *name)
{
int i, len, lines=TT.lines, size=sizeof(toybuf);
if (toys.optc > 1) {
// Print an extra newline for all but the first file
if (TT.file_no++) xprintf("\n");
xprintf("==> %s <==\n", name);
xflush();
}
while (lines) {
len = read(fd, toybuf, size);
if (len<0) perror_msg("%s",name);
if (len<1) break;
for(i=0; i<len;) if (toybuf[i++] == '\n' && !--lines) break;
xwrite(1, toybuf, i);
}
}
void head_main(void)
{
char *arg = *toys.optargs;
// handle old "-42" style arguments
if (arg && *arg == '-' && arg[1]) {
TT.lines = atolx(arg+1);
toys.optc--;
} else arg = 0;
loopfiles(toys.optargs+!!arg, do_head);
}
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