--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/template/grep.c	Tue Jul 06 05:39:41 2010 +0900
@@ -0,0 +1,84 @@
+/* Excerpted from 'The Practice of Programming' */
+/* by Brian W. Kernighan and Rob Pike */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define BUFSIZE 1024
+
+int match(char *regexp, char *text) {
+  if (regexp[0] == '^')
+    return matchhere(regexp+1, text);
+  do {
+    if (matchhere(regexp+1, text))
+      return 1;
+  } while (*text++ != '\0');
+  return 0;
+}
+
+int matchhere(char *regexp, char *text) {
+  if (regexp[0] == '\0')
+    return 1;
+  if (regexp[1] == '*')
+    return matchstar(regexp[0], regexp+2, text);
+  if (regexp[0] == '$' && regexp[1] == '\0')
+    return *text == '\0';
+  if (*text != '\0' && (regexp[0] == '.' || regexp[0] == *text))
+    return matchhere(regexp+1, text+1);
+  return 0;
+}
+
+int matchstar(int c, char *regexp, char *text) {
+  do {
+    if (matchhere(regexp, text))
+      return 1;
+  } while (*text != '\0' && (*text++ == c || c == '.'));
+  return 0;
+}
+
+int grep(char * regexp, FILE *f, char *name) {
+  int n, nmatch;
+  char buf[BUFSIZE];
+  nmatch = 0;
+  while (fgets(buf, sizeof buf, f) != NULL) {
+    n = strlen(buf);
+    if (n > 0 && buf[n-1] == '\n')
+      buf[n-1] = '\0';
+    if (match(regexp, buf)) {
+      nmatch++;
+      if (name != NULL)
+        printf("%s:", name);
+      printf("%s\n", buf);
+    }
+  }
+  return nmatch;
+}
+
+int main(int argc, char* argv[]) {
+  int i, nmatch;
+  FILE *f;
+
+  if (argc < 2) {
+    fprintf(stderr, "usage: grep regexp [file ...]");
+    exit(0);
+  }
+  nmatch = 0;
+  if (argc == 2) {
+    if (grep(argv[1], stdin, NULL))
+      nmatch;
+  } else {
+    for (i = 2; i < argc; i++) {
+      f = fopen(argv[i], "r");
+      if (f == NULL) {
+        fprintf(stderr, "can't open %s:", argv[i]);
+        continue;
+      }
+      if (grep(argv[1], f, argc > 3 ? argv[i] : NULL) > 0)
+        nmatch++;
+      fclose(f);
+    }
+  }
+
+  return nmatch;
+}