On Thu, Dec 07, 2017 at 05:36:59PM +0200, Paul Irofti wrote:
> Hi,
>
> The -m, or --max-count, option allows the user to stop grep(1)
> processing after a given number of matches are found.
> If you use constructs such as
>
> $ grep foo foo.txt | head -n1
>
> you will want to use the much faster version
>
> $ grep -m1 foo foo.txt
>
> This option already exists in at least Linux, FreeBSD and NetBSD.
>
> For example, I need grep -m for vimtex (see Issue #1018 on GitHub[0]).
> But, if I had known that this exists, I would have used it in the
> past with other scripts.
>
> The following diff is adapted from FreeBSD and I tested it with vimtex
> and a few hand-crafted examples. We could probably do some tricks with
> mcount and mlimit, but I do not think it is worth it. OK?
>
> [0] -- https://github.com/lervag/vimtex/issues/1018
Here is a new diff that corrects usage to show that -m expects an
argument (as suggested by deraadt@) and also adds the manpage bits.
Index: grep.1
===================================================================
RCS file: /cvs/src/usr.bin/grep/grep.1,v
retrieving revision 1.43
diff -u -p -u -p -r1.43 grep.1
--- grep.1 13 Jan 2015 04:45:34 -0000 1.43
+++ grep.1 7 Dec 2017 18:00:37 -0000
@@ -44,6 +44,7 @@
.Op Fl C Ns Op Ar num
.Op Fl e Ar pattern
.Op Fl f Ar file
+.Op Fl m Ar num
.Op Fl -binary-files Ns = Ns Ar value
.Op Fl -context Ns Op = Ns Ar num
.Op Fl -line-buffered
@@ -216,6 +217,10 @@ Pathnames are listed once per file searc
If the standard input is searched, the string
.Dq (standard input)
is written.
+.It Fl m Ar num
+Stop after
+.Ar num
+matches.
.It Fl n
Each output line is preceded by its relative line number in the file,
starting at line 1.
Index: grep.c
===================================================================
RCS file: /cvs/src/usr.bin/grep/grep.c,v
retrieving revision 1.55
diff -u -p -u -p -r1.55 grep.c
--- grep.c 28 Nov 2015 01:17:12 -0000 1.55
+++ grep.c 7 Dec 2017 18:00:38 -0000
@@ -71,6 +71,9 @@ int cflag; /* -c: only show a count of
int hflag; /* -h: don't print filename headers */
int iflag; /* -i: ignore case */
int lflag; /* -l: only show names of files with matches */
+int mflag; /* -m x: stop reading the files after x matches */
+long long mcount; /* count for -m */
+long long mlimit; /* requested value for -m */
int nflag; /* -n: show line numbers in front of matching lines */
int oflag; /* -o: print each match */
int qflag; /* -q: quiet mode (don't output anything) */
@@ -111,15 +114,16 @@ usage(void)
#else
"usage: %s [-abcEFGHhIiLlnoqRsUVvwxZ] [-A num] [-B num] [-C[num]]\n"
#endif
- "\t[-e pattern] [-f file] [--binary-files=value]
[--context[=num]]\n"
- "\t[--line-buffered] [pattern] [file ...]\n", __progname);
+ "\t[-e pattern] [-f file] [-m num] [--binary-files=value]\n"
+ "\t[--context[=num]] [--line-buffered] [pattern] [file ...]\n",
+ __progname);
exit(2);
}
#ifdef NOZ
-static const char optstr[] = "0123456789A:B:CEFGHILRUVabce:f:hilnoqrsuvwxy";
+static const char optstr[] = "0123456789A:B:CEFGHILRUVabce:f:hilm:noqrsuvwxy";
#else
-static const char optstr[] = "0123456789A:B:CEFGHILRUVZabce:f:hilnoqrsuvwxy";
+static const char optstr[] = "0123456789A:B:CEFGHILRUVZabce:f:hilm:noqrsuvwxy";
#endif
static const struct option long_options[] =
@@ -147,6 +151,7 @@ static const struct option long_options[
{"ignore-case", no_argument, NULL, 'i'},
{"files-without-match", no_argument, NULL, 'L'},
{"files-with-matches", no_argument, NULL, 'l'},
+ {"max-count", required_argument, NULL, 'm'},
{"line-number", no_argument, NULL, 'n'},
{"quiet", no_argument, NULL, 'q'},
{"silent", no_argument, NULL, 'q'},
@@ -375,6 +380,14 @@ main(int argc, char *argv[])
case 'l':
Lflag = 0;
lflag = qflag = 1;
+ break;
+ case 'm':
+ mflag = 1;
+ errno = 0;
+ mlimit = mcount = strtonum(optarg, 1, LLONG_MAX,
+ &errstr);
+ if (errstr != NULL)
+ errx(2, "mcount %s", errstr);
break;
case 'n':
nflag = 1;
Index: grep.h
===================================================================
RCS file: /cvs/src/usr.bin/grep/grep.h,v
retrieving revision 1.24
diff -u -p -u -p -r1.24 grep.h
--- grep.h 14 Dec 2015 20:02:07 -0000 1.24
+++ grep.h 7 Dec 2017 18:00:38 -0000
@@ -66,14 +66,17 @@ extern int cflags, eflags;
/* Command line flags */
extern int Aflag, Bflag, Eflag, Fflag, Hflag, Lflag,
Rflag, Zflag,
- bflag, cflag, hflag, iflag, lflag, nflag, oflag, qflag, sflag,
- vflag, wflag, xflag;
+ bflag, cflag, hflag, iflag, lflag, mflag, nflag, oflag, qflag,
+ sflag, vflag, wflag, xflag;
extern int binbehave;
extern int first, matchall, patterns, tail, file_err;
extern char **pattern;
extern fastgrep_t *fg_pattern;
extern regex_t *r_pattern;
+
+/* For -m max-count */
+extern long long mcount, mlimit;
/* For regex errors */
#define RE_ERROR_BUF 512
Index: util.c
===================================================================
RCS file: /cvs/src/usr.bin/grep/util.c,v
retrieving revision 1.57
diff -u -p -u -p -r1.57 util.c
--- util.c 3 Apr 2017 16:18:35 -0000 1.57
+++ util.c 7 Dec 2017 18:00:38 -0000
@@ -97,6 +97,8 @@ procfile(char *fn)
file_t *f;
int c, t, z, nottext;
+ mcount = mlimit;
+
if (fn == NULL) {
fn = "(standard input)";
f = grep_fdopen(STDIN_FILENO, "r");
@@ -140,6 +142,8 @@ procfile(char *fn)
linesqueued++;
}
c += t;
+ if (mflag && mcount <= 0)
+ break;
}
if (Bflag > 0)
clearqueue();
@@ -223,6 +227,10 @@ redo:
print:
if (vflag)
c = !c;
+
+ /* Count the matches if we have a match limit */
+ if (mflag)
+ mcount -= c;
if (c && binbehave == BIN_FILE_BIN && nottext)
return c; /* Binary file */
