Add the m option (from grep).

doc/agrep.1.in

@@ -115,6 +115,52 @@ environment variable.  The default color is red.
 Only print a count of matching records per each input file,
 suppressing normal output.
 .TP
+.BI \-m " NUM" "\fR,\fP \-\^\-max\-count=" NUM
+Stop reading a file after
+.I NUM
+matching lines.
+If
+.I NUM
+is zero,
+.B agrep
+stops right away without reading input.
+A
+.I NUM
+of \-1 is treated as infinity and
+.B agrep
+does not stop; this is the default.
+If the input is standard input from a regular file,
+and
+.I NUM
+matching lines are output,
+.B agrep
+ensures that the standard input is positioned to just after the last
+matching line before exiting, regardless of the presence of trailing
+context lines.
+This enables a calling process to resume a search.
+When
+.B agrep
+stops after
+.I NUM
+matching lines, it outputs any trailing context lines.
+When the
+.B \-c
+or
+.B \-\^\-count
+option is also used,
+.B agrep
+does not output a count greater than
+.IR NUM .
+When the
+.B \-v
+or
+.B \-\^\-invert\-match
+option is also used,
+.B agrep
+stops after outputting
+.I NUM
+non-matching lines.
+.TP
 .BR \-h ", " \-\^\-no\-filename
 Suppress the prefixing filename on output when multiple files are
 searched.

src/agrep.c

@@ -44,7 +44,7 @@
 
 /* Short options. */
 static char const short_options[] =
-"cd:e:hiklnqsvwyBD:E:HI:MS:V0123456789-:";
+"cd:e:hiklm:nqsvwyBD:E:HI:MS:V0123456789-:";
 
 static int show_help;
 char *program_name;
@@ -72,6 +72,7 @@ static struct option const long_options[] =
   {"insert-cost", required_argument, NULL, 'I'},
   {"invert-match", no_argument, NULL, 'v'},
   {"line-number", no_argument, NULL, 'n'},
+  {"max-count", required_argument, NULL, 'm'},
   {"literal", no_argument, NULL, 'k'},
   {"max-errors", required_argument, NULL, 'E'},
   {"no-filename", no_argument, NULL, 'h'},
@@ -139,6 +140,7 @@ Output control:\n\
   -H, --with-filename	    print the filename for each match\n\
   -l, --files-with-matches  only print FILE names containing matches\n\
   -M, --delimiter-after     print record delimiter after record if -d is used\n\
+  -m, --max-count=NUM       stop after NUM selected lines\n\
   -n, --record-number	    print record number with output\n\
       --line-number         same as -n\n\
   -q, --quiet, --silent	    suppress all normal output\n\
@@ -185,6 +187,8 @@ static int print_filename; /* Output filename. */
 static int print_recnum;   /* Output record number. */
 static int print_cost;	   /* Output match cost. */
 static int count_matches;  /* Count matching records. */
+static int max_count; /* Max number of selected
+                                   lines from an input file.  */
 static int list_files;	   /* List matching files. */
 static int color_option;   /* Highlight matches. */
 static int print_position;  /* Show start and end offsets for matches. */
@@ -449,6 +453,11 @@ tre_agrep_handle_file(const char *filename)
 		  printf("%.*s", record_len, record);
 		}
 	    }
+            /* exit after max_count match(es) */
+            if((max_count > 0)&&(count > (max_count-1))) {
+              if(count_matches) break;/* to get the result */
+              else exit(0);/* to leave the stream "as is" */
+            }
 	}
     }
 
@@ -498,6 +507,7 @@ main(int argc, char **argv)
   be_silent = 0;
   tre_regaparams_default(&match_params);
   match_params.max_cost = 0;
+  max_count = -1;
 
   /* Parse command line options. */
   while (1)
@@ -542,6 +552,10 @@ main(int argc, char **argv)
 	  /* Only print files that contain matches. */
 	  list_files = 1;
 	  break;
+        case 'm':
+          /* stop after n selected lines */
+          max_count = atoi(optarg);
+          break;
 	case 'n':
 	  /* Print record number of matching record. */
 	  print_recnum = 1;
@@ -652,6 +666,10 @@ Copyright (c) 2001-2009 Ville Laurikari <vl@iki.fi>.\n"));
   if (show_help)
     tre_agrep_usage(0);
 
+  /* Fail without reading if count number is 0 */
+  if (max_count == 0)
+    return EXIT_FAILURE;
+
   if (color_option)
     {
       char *user_highlight = getenv("GREP_COLOR");