freebsd-skq/bin/echo/echo.c
dds cbf5708f43 - Check and report write(2) errors.
- Issue a single writev(2) call instead of multiple write(2)s.
  This change improves the inefficiencies introduced when echo
  went on an stdio diet.

The following figures are for echoing 1000 arguments.
original stdio-based echo:
        0.01 real         0.01 user         0.00 sys
before:
        0.05 real         0.00 user         0.04 sys
after:
        0.01 real         0.00 user         0.00 sys
2003-10-11 20:34:43 +00:00

142 lines
4.1 KiB
C

/*
* Copyright (c) 1989, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if 0
#ifndef lint
static char const copyright[] =
"@(#) Copyright (c) 1989, 1993\n\
The Regents of the University of California. All rights reserved.\n";
#endif /* not lint */
#ifndef lint
static char sccsid[] = "@(#)echo.c 8.1 (Berkeley) 5/31/93";
#endif /* not lint */
#endif
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/uio.h>
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
/*
* Report an error and exit.
* Use it instead of err(3) to avoid linking-in stdio.
*/
static void
errexit(const char *prog, const char *reason)
{
char *errstr = strerror(errno);
write(STDERR_FILENO, prog, strlen(prog));
write(STDERR_FILENO, ": ", 2);
write(STDERR_FILENO, reason, strlen(reason));
write(STDERR_FILENO, ": ", 2);
write(STDERR_FILENO, errstr, strlen(errstr));
write(STDERR_FILENO, "\n", 1);
exit(1);
}
int
main(int argc, char *argv[])
{
int nflag; /* if not set, output a trailing newline. */
int veclen; /* number of writev arguments. */
struct iovec *iov, *vp; /* Elements to write, current element. */
char space[] = " ";
char newline[] = "\n";
char *progname = argv[0];
/* This utility may NOT do getopt(3) option parsing. */
if (*++argv && !strcmp(*argv, "-n")) {
++argv;
--argc;
nflag = 1;
} else
nflag = 0;
veclen = (argc >= 2) ? (argc - 2) * 2 + 1 : 0;
if ((vp = iov = malloc((veclen + 1) * sizeof(struct iovec))) == NULL)
errexit(progname, "malloc");
while (argv[0] != NULL) {
size_t len;
len = strlen(argv[0]);
/*
* If the next argument is NULL then this is this
* the last argument, therefore we need to check
* for a trailing \c.
*/
if (argv[1] == NULL) {
/* is there room for a '\c' and is there one? */
if (len >= 2 &&
argv[0][len - 2] == '\\' &&
argv[0][len - 1] == 'c') {
/* chop it and set the no-newline flag. */
len -= 2;
nflag = 1;
}
}
vp->iov_base = *argv;
vp++->iov_len = len;
if (*++argv) {
vp->iov_base = space;
vp++->iov_len = 1;
}
}
if (!nflag) {
veclen++;
vp->iov_base = newline;
vp++->iov_len = 1;
}
/* assert(veclen == (vp - iov)); */
while (veclen) {
int nwrite;
nwrite = (veclen > IOV_MAX) ? IOV_MAX : veclen;
if (writev(STDOUT_FILENO, iov, nwrite) == -1)
errexit(progname, "write");
iov += nwrite;
veclen -= nwrite;
}
return 0;
}