--- grep-3.1-orig/grep-3.1/src/grep.c	2017-07-02 13:41:41.000000000 -0400
+++ grep-3.1/src/grep.c	2018-03-29 18:01:35.556895798 -0400
@@ -21,6 +21,8 @@
 #include <config.h>
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
+#include <string.h>
 #include <wchar.h>
 #include <fcntl.h>
 #include <inttypes.h>
@@ -414,7 +416,7 @@
 static struct exclude *excluded_directory_patterns[2];
 /* Short options.  */
 static char const short_options[] =
-"0123456789A:B:C:D:EFGHIPTUVX:abcd:e:f:hiLlm:noqRrsuvwxyZz";
+"0123456789A:B:C:D:EFGHIPTUVX:abcd:e:f:hiLlm:noqRrsuvwxyZzp:";
 
 /* Non-boolean long options that have no corresponding short equivalents.  */
 enum
@@ -483,6 +485,7 @@
   {"version", no_argument, NULL, 'V'},
   {"with-filename", no_argument, NULL, 'H'},
   {"word-regexp", no_argument, NULL, 'w'},
+  {"preprocess", required_argument, NULL, 'p'},
   {0, 0, 0, 0}
 };
 
@@ -534,6 +537,9 @@
     SKIP_DEVICES
   } devices = READ_COMMAND_LINE_DEVICES;
 
+static char *preproc;    /* if non-NULL pipe each file input to this command */
+static pid_t preprocPID; /* current preproc decoder child PID to wait for. */
+
 static bool grepfile (int, char const *, bool, bool);
 static bool grepdesc (int, bool);
 
@@ -1702,6 +1708,40 @@
         suppressible_error (errno);
       return true;
     }
+  if (preproc) {          /* desc <- preprocessing decoder output */
+    int fds[2], ac = 0;
+    char *sh, *av[5 + 3];
+    if (pipe (fds) == -1)
+      exit (2);
+    switch (preprocPID = vfork ()) {
+      case 0:             /* child */
+        dup2 (desc, 0);   /* stdin = desc on file itself */
+        dup2 (fds[1], 1); /* stdout = write end of pipe [1] */
+        close (fds[1]);   /* do not need extra handle on pipe */
+        close (fds[0]);   /* close read end of pipe [0] */
+        setenv ("GREP_INPUT", filename, 1);
+        if (!(sh = getenv ("GREP_SHELL")))
+          sh = "/bin/sh";
+        ac = 0;           /* word-split $GREP_SHELL a few times */
+        av[ac] = strtok (sh, " \t");
+        for (ac++; ac < 5; ac++)
+          if (!(av[ac] = strtok (NULL, " \t")))
+            break;
+        av[ac++] = "-c";  /* append -c preproc */
+        av[ac++] = preproc;
+        av[ac] = NULL;
+        execvp (av[0], av); /* become a preprocessing decoder */
+        fprintf (stderr, "%s -c \"%s\": %s\n", sh, preproc, strerror (errno));
+        exit (3);
+      default:            /* parent */
+        close (fds[1]);   /* close write end of pipe[1] */
+        close (desc);     /* close desc on file itself */
+        desc = fds[0];    /* replace desc value with read end of pipe [0] */
+        break;
+      case -1: /* vfork failed => resource exhaustion => die */
+        exit (2);
+    }
+  }
   return grepdesc (desc, command_line);
 }
 
@@ -1876,6 +1916,19 @@
     }
 
  closeout:
+  if (preprocPID) {
+    int wstatus = 0;
+    /* Do not decode whole file if it won't be read anyway, e.g. -l mode. */
+    kill (preprocPID, SIGKILL); /* waitpid NOHANG before killing? */
+    while (waitpid (preprocPID, &wstatus, 0) == -1)
+      if (errno != EINTR)
+        break;
+    if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) != EXIT_SUCCESS)
+      exit (2); /* post-signal status == success; only get here on cmd fail */
+    preprocPID = 0;
+    /*XXX verify that signal was SIGKILL and perhaps die otherwise? */
+  }
+
   if (desc != STDIN_FILENO && close (desc) != 0)
     suppressible_error (errno);
   return status;
@@ -1957,6 +2010,7 @@
 "));
       printf (_("\
   -I                        equivalent to --binary-files=without-match\n\
+  -p, --preprocess=COMMAND  pipe file inputs to stdin of COMMAND pre-search\n\
   -d, --directories=ACTION  how to handle directories;\n\
                             ACTION is 'read', 'recurse', or 'skip'\n\
   -D, --devices=ACTION      how to handle devices, FIFOs and sockets;\n\
@@ -2676,6 +2730,10 @@
         eolbyte = '\0';
         break;
 
+      case 'p':
+        preproc = optarg;
+        break;
+
       case BINARY_FILES_OPTION:
         if (STREQ (optarg, "binary"))
           binary_files = BINARY_BINARY_FILES;
--- grep-3.1-orig/grep-3.1/doc/grep.in.1	2017-06-24 23:05:03.000000000 -0400
+++ grep-3.1/doc/grep.in.1	2018-03-29 17:55:56.579906789 -0400
@@ -462,6 +462,30 @@
 in the environment, in order to find more matches even if the matches
 are unsafe for direct display.
 .TP
+.BI \-p " COMMAND" "\fR,\fP \-\^\-preprocess=" COMMAND
+If this option is given, for each input file
+.I COMMAND
+is invoked with that input file as standard input and with grep reading
+and searching the standard output of
+.I COMMAND
+instead of direct file contents.  E.g., if
+.I COMMAND
+is
+.RB "\*(lq" "gzip -dc" "\*(rq"
+grep will decompress each file before searching it, assuming all
+inputs are gzipped.
+.I COMMAND
+is run via \fB${GREP_SHELL:-/bin/sh} -c COMMAND\fR.
+.IP
+The environment variable GREP_INPUT set to each input filename.
+This may be useful to dispatch to appropriate decoders.
+E.g., with a standard shell, (note single/double quoting),
+.nf
+  GPP='case "$GREP_INPUT" in *.gz) gzip -dc;; *) cat;; esac'
+.fi
+will allow \fB grep -p"$GPP"\fR to search through a mixture of
+gzipped and ordinary files.
+.TP
 .BI \-D " ACTION" "\fR,\fP \-\^\-devices=" ACTION
 If an input file is a device, FIFO or socket, use
 .I ACTION
@@ -1187,7 +1211,7 @@
 .SH "SEE ALSO"
 .SS "Regular Manual Pages"
 awk(1), cmp(1), diff(1), find(1), gzip(1),
-perl(1), sed(1), sort(1), xargs(1), zgrep(1),
+perl(1), sed(1), sort(1), xargs(1), zgrep(1), gunzip(1),
 read(2),
 pcre(3), pcresyntax(3), pcrepattern(3),
 terminfo(5),