- 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
This commit is contained in:
parent
84b11cd80a
commit
91b7d6dc58
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=121010
@ -45,23 +45,56 @@ static char sccsid[] = "@(#)echo.c 8.1 (Berkeley) 5/31/93";
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <unistd.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/uio.h>
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#include <assert.h>
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#include <errno.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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/*
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* Report an error and exit.
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* Use it instead of err(3) to avoid linking-in stdio.
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*/
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static void
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errexit(const char *prog, const char *reason)
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{
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char *errstr = strerror(errno);
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write(STDERR_FILENO, prog, strlen(prog));
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write(STDERR_FILENO, ": ", 2);
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write(STDERR_FILENO, reason, strlen(reason));
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write(STDERR_FILENO, ": ", 2);
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write(STDERR_FILENO, errstr, strlen(errstr));
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write(STDERR_FILENO, "\n", 1);
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exit(1);
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}
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/* ARGSUSED */
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int
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main(int argc __unused, char *argv[])
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main(int argc, char *argv[])
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{
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int nflag; /* if not set, output a trailing newline. */
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int veclen; /* number of writev arguments. */
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struct iovec *iov, *vp; /* Elements to write, current element. */
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char space[] = " ";
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char newline[] = "\n";
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char *progname = argv[0];
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/* This utility may NOT do getopt(3) option parsing. */
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if (*++argv && !strcmp(*argv, "-n")) {
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++argv;
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--argc;
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nflag = 1;
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}
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else
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} else
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nflag = 0;
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veclen = (argc >= 2) ? (argc - 2) * 2 + 1 : 0;
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if ((vp = iov = malloc((veclen + 1) * sizeof(struct iovec))) == NULL)
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errexit(progname, "malloc");
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while (argv[0] != NULL) {
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size_t len;
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@ -82,11 +115,27 @@ main(int argc __unused, char *argv[])
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nflag = 1;
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}
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}
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write(STDOUT_FILENO, argv[0], len);
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if (*++argv)
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write(STDOUT_FILENO, " ", 1);
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vp->iov_base = *argv;
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vp++->iov_len = len;
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if (*++argv) {
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vp->iov_base = space;
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vp++->iov_len = 1;
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}
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}
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if (!nflag) {
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veclen++;
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vp->iov_base = newline;
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vp++->iov_len = 1;
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}
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/* assert(veclen == (vp - iov)); */
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while (veclen) {
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int nwrite;
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nwrite = (veclen > IOV_MAX) ? IOV_MAX : veclen;
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if (writev(STDOUT_FILENO, iov, nwrite) == -1)
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errexit(progname, "write");
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iov += nwrite;
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veclen -= nwrite;
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}
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if (!nflag)
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write(STDOUT_FILENO, "\n", 1);
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return 0;
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}
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