grep: implement -m MAX_MATCHES; fix help text

grep_file                                            771     822     +51
packed_usage                                       22573   22610     +37
.rodata                                           128058  128090     +32
grep_main                                            842     853     +11
max_matches                                            -       4      +4
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 4/0 up/down: 135/0)             Total: 135 bytes

2 files changed, 49 insertions, 39 deletions

diff --git a/findutils/grep.c b/findutils/grep.c
index 7bade87..e543ee0 100644
--- a/findutils/grep.c
+++ b/findutils/grep.c
@@ -24,7 +24,7 @@
 
 /* options */
 #define OPTSTR_GREP \
-	"lnqvscFiHhe:f:Lor" \
+	"lnqvscFiHhe:f:Lorm:" \
 	USE_FEATURE_GREP_CONTEXT("A:B:C:") \
 	USE_FEATURE_GREP_EGREP_ALIAS("E") \
 	USE_DESKTOP("w") \
@@ -33,26 +33,27 @@
 /* ignored: -I "assume binary files have no matches" */
 
 enum {
-	OPTBIT_l,
-	OPTBIT_n,
-	OPTBIT_q,
-	OPTBIT_v,
-	OPTBIT_s,
-	OPTBIT_c,
-	OPTBIT_F,
-	OPTBIT_i,
-	OPTBIT_H,
-	OPTBIT_h,
-	OPTBIT_e,
-	OPTBIT_f,
-	OPTBIT_L,
-	OPTBIT_o,
-	OPTBIT_r,
-	USE_FEATURE_GREP_CONTEXT(    OPTBIT_A ,)
-	USE_FEATURE_GREP_CONTEXT(    OPTBIT_B ,)
-	USE_FEATURE_GREP_CONTEXT(    OPTBIT_C ,)
-	USE_FEATURE_GREP_EGREP_ALIAS(OPTBIT_E ,)
-	USE_DESKTOP(                 OPTBIT_w ,)
+	OPTBIT_l, /* list matched file names only */
+	OPTBIT_n, /* print line# */
+	OPTBIT_q, /* quiet - exit(0) of first match */
+	OPTBIT_v, /* invert the match, to select non-matching lines */
+	OPTBIT_s, /* suppress errors about file open errors */
+	OPTBIT_c, /* count matches per file (suppresses normal output) */
+	OPTBIT_F, /* literal match */
+	OPTBIT_i, /* case-insensitive */
+	OPTBIT_H, /* force filename display */
+	OPTBIT_h, /* inhibit filename display */
+	OPTBIT_e, /* -e PATTERN */
+	OPTBIT_f, /* -f FILE_WITH_PATTERNS */
+	OPTBIT_L, /* list unmatched file names only */
+	OPTBIT_o, /* show only matching parts of lines */
+	OPTBIT_r, /* recurse dirs */
+	OPTBIT_m, /* -m MAX_MATCHES */
+	USE_FEATURE_GREP_CONTEXT(    OPTBIT_A ,) /* -A NUM: after-match context */
+	USE_FEATURE_GREP_CONTEXT(    OPTBIT_B ,) /* -B NUM: before-match context */
+	USE_FEATURE_GREP_CONTEXT(    OPTBIT_C ,) /* -C NUM: -A and -B combined */
+	USE_FEATURE_GREP_EGREP_ALIAS(OPTBIT_E ,) /* extended regexp */
+	USE_DESKTOP(                 OPTBIT_w ,) /* whole word match */
 	OPT_l = 1 << OPTBIT_l,
 	OPT_n = 1 << OPTBIT_n,
 	OPT_q = 1 << OPTBIT_q,
@@ -68,6 +69,7 @@ enum {
 	OPT_L = 1 << OPTBIT_L,
 	OPT_o = 1 << OPTBIT_o,
 	OPT_r = 1 << OPTBIT_r,
+	OPT_m = 1 << OPTBIT_m,
 	OPT_A = USE_FEATURE_GREP_CONTEXT(    (1 << OPTBIT_A)) + 0,
 	OPT_B = USE_FEATURE_GREP_CONTEXT(    (1 << OPTBIT_B)) + 0,
 	OPT_C = USE_FEATURE_GREP_CONTEXT(    (1 << OPTBIT_C)) + 0,
@@ -85,6 +87,7 @@ enum {
 
 typedef unsigned char byte_t;
 
+static int max_matches;
 static int reflags;
 static byte_t invert_search;
 static byte_t print_filename;
@@ -97,7 +100,6 @@ static int lines_after;
 static char **before_buf;
 static int last_line_printed;
 #endif /* ENABLE_FEATURE_GREP_CONTEXT */
-
 /* globals used internally */
 static llist_t *pattern_head;   /* growable list of patterns to match */
 static const char *cur_file;    /* the current file we are reading */
@@ -146,6 +148,8 @@ static int grep_file(FILE *file)
 	int print_n_lines_after = 0;
 	int curpos = 0; /* track where we are in the circular 'before' buffer */
 	int idx = 0; /* used for iteration through the circular buffer */
+#else
+	enum { print_n_lines_after = 0 };
 #endif /* ENABLE_FEATURE_GREP_CONTEXT */
 
 	while ((line = xmalloc_getline(file)) != NULL) {
@@ -212,6 +216,12 @@ static int grep_file(FILE *file)
 				return 1; /* one match */
 			}
 
+#if ENABLE_FEATURE_GREP_CONTEXT
+			/* Were we printing context and saw next (unwanted) match? */
+			if ((option_mask32 & OPT_m) && nmatches > max_matches)
+				break;
+#endif
+
 			/* print the matched line */
 			if (PRINT_MATCH_COUNTS == 0) {
 #if ENABLE_FEATURE_GREP_CONTEXT
@@ -255,7 +265,7 @@ static int grep_file(FILE *file)
 #if ENABLE_FEATURE_GREP_CONTEXT
 		else { /* no match */
 			/* if we need to print some context lines after the last match, do so */
-			if (print_n_lines_after /* && (last_line_printed != linenum) */ ) {
+			if (print_n_lines_after) {
 				print_line(line, linenum, '-');
 				print_n_lines_after--;
 			} else if (lines_before) {
@@ -264,12 +274,17 @@ static int grep_file(FILE *file)
 				before_buf[curpos] = line;
 				curpos = (curpos + 1) % lines_before;
 				/* avoid free(line) - we took line */
-				continue;
+				line = NULL;
 			}
 		}
 
 #endif /* ENABLE_FEATURE_GREP_CONTEXT */
 		free(line);
+
+		/* Did we print all context after last requested match? */
+		if ((option_mask32 & OPT_m)
+		 && !print_n_lines_after && nmatches == max_matches)
+			break;
 	}
 
 	/* special-case file post-processing for options where we don't print line
@@ -311,7 +326,6 @@ static char * add_grep_list_data(char *pattern)
 	return (char *)gl;
 }
 
-
 static void load_regexes_from_file(llist_t *fopt)
 {
 	char *line;
@@ -365,6 +379,7 @@ int grep_main(int argc, char **argv)
 {
 	FILE *file;
 	int matched;
+	char *mopt;
 	llist_t *fopt = NULL;
 
 	/* do normal option parsing */
@@ -376,7 +391,7 @@ int grep_main(int argc, char **argv)
 	opt_complementary = "H-h:e::f::C-AB";
 	getopt32(argc, argv,
 		OPTSTR_GREP,
-		&pattern_head, &fopt,
+		&pattern_head, &fopt, &mopt,
 		&slines_after, &slines_before, &Copt);
 
 	if (option_mask32 & OPT_C) {
@@ -405,8 +420,11 @@ int grep_main(int argc, char **argv)
 	/* with auto sanity checks */
 	opt_complementary = "H-h:e::f::c-n:q-n:l-n";
 	getopt32(argc, argv, OPTSTR_GREP,
-		&pattern_head, &fopt);
+		&pattern_head, &fopt, &mopt);
 #endif
+	if (option_mask32 & OPT_m) {
+		max_matches = xatoi_u(mopt);
+	}
 	invert_search = ((option_mask32 & OPT_v) != 0); /* 0 | 1 */
 
 	if (pattern_head != NULL) {
@@ -487,12 +505,7 @@ int grep_main(int argc, char **argv)
 		}
 		matched += grep_file(file);
 		fclose_if_not_stdin(file);
- grep_done:
-		if (matched < 0) {
-			/* we found a match but were told to be quiet, stop here and
-			* return success */
-			break;
-		}
+ grep_done: ;
 	}
 
 	/* destroy all the elments in the pattern list */
@@ -512,10 +525,6 @@ int grep_main(int argc, char **argv)
 		}
 	}
 	/* 0 = success, 1 = failed, 2 = error */
-	/* If the -q option is specified, the exit status shall be zero
-	 * if an input line is selected, even if an error was detected.  */
-	if (BE_QUIET && matched)
-		return 0;
 	if (open_errors)
 		return 2;
 	return !matched; /* invert return value 0 = success, 1 = failed */
diff --git a/include/usage.h b/include/usage.h
index 6832504..bd9cb99 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -1164,14 +1164,15 @@
        "\n	-v	Select non-matching lines" \
        "\n	-s	Suppress file open/read error messages" \
        "\n	-c	Only print count of matching lines" \
-       "\n	-f	Read PATTERN from file" \
        "\n	-o	Show only the part of a line that matches PATTERN" \
+       "\n	-m MAX	Match up to MAX times per file" \
 	USE_DESKTOP( \
        "\n	-w	Match whole words only") \
-       "\n	-e	PATTERN is a regular expression" \
        "\n	-F	PATTERN is a set of newline-separated strings" \
 	USE_FEATURE_GREP_EGREP_ALIAS( \
        "\n	-E	PATTERN is an extended regular expression") \
+       "\n	-e PTRN	Pattern to match" \
+       "\n	-f FILE	Read pattern from file" \
 	USE_FEATURE_GREP_CONTEXT( \
        "\n	-A	Print NUM lines of trailing context" \
        "\n	-B	Print NUM lines of leading context" \