bore

commit a90d2148edb9b10b6b3c1b889d4e8a7b0d344c9d
parent 53a9fb34af443290a5283505b582f82159f98c7c
Author: phoebos <ben@bvnf.space>
Date:   Thu,  9 Dec 2021 01:55:38 +0000

grep: add basic grep

Diffstat:
M
Makefile
 | 
1
+
M
PROGRESS
 | 
2
+-
A
grep.c
 | 
139
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

3 files changed, 141 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
@@ -5,6 +5,7 @@ BINS = \
 	echo \
 	ed \
 	false \
+	grep \
 	head \
 	ls \
 	mkdir \
diff --git a/PROGRESS b/PROGRESS
@@ -17,7 +17,7 @@
 [ ] ed [-ps] p i a q Q
 [x] false
 [ ] find
-[ ] grep
+[ ] grep [-icv]
 [x] head [-n]
 [ ] id
 [ ] kill
diff --git a/grep.c b/grep.c
@@ -0,0 +1,139 @@
+#include <errno.h>
+#include <limits.h>
+#include <regex.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+enum {
+    FLAG_c = 1 << 0,
+    FLAG_v = 1 << 1,
+};
+
+int
+match(const char *string, regex_t *re) {
+    int status = regexec(re, string, 0, NULL, 0);
+
+    if (status != 0)
+        return 0;
+    return 1;
+}
+
+int
+grep(FILE *f, regex_t *re, int flags) {
+    size_t len = LINE_MAX;
+    ssize_t bytes;
+    char *buf = malloc(len);
+    if (buf == NULL) {
+        fprintf(stderr, "grep: %s\n", strerror(errno));
+        return 1;
+    }
+
+    int num_matches = 0;
+    while ((bytes = getline(&buf, &len, f)) != -1) {
+        int matches = match(buf, re);
+        if ((matches && ! (flags & FLAG_v)) || (! matches && (flags & FLAG_v))) {
+            num_matches++;
+            if (! (flags & FLAG_c) && write(1, buf, bytes) == -1) {
+                fprintf(stderr, "grep: %s\n", strerror(errno));
+                return 1;
+            }
+        }
+    }
+
+    if (flags & FLAG_c)
+        printf("%d\n", num_matches);
+
+    if (ferror(f)) {
+        fprintf(stderr, "grep: %s\n", strerror(errno));
+        return 1;
+    }
+    free(buf);
+
+    if (num_matches == 0)
+        return 1;
+    return 0;
+}
+
+void
+print_usage(void) {
+    fprintf(stderr, "usage: grep [-E|-F] [-icv] regexp [file...]\n");
+}
+
+int
+main(int argc, char **argv) {
+    int ret = 1;
+
+    int c;
+    int REGFLAGS = REG_NOSUB;
+    int flags = 0;
+    while ((c = getopt(argc, argv, "EFchiv")) != -1) {
+        switch (c) {
+            case 'E':
+                REGFLAGS |= REG_EXTENDED;
+                break;
+            case 'F':
+                REGFLAGS &= ~REG_EXTENDED;
+                break;
+            case 'c':
+                flags |= FLAG_c;
+                break;
+            case 'h':
+                print_usage();
+                return 0;
+            case 'i':
+                REGFLAGS |= REG_ICASE;
+                break;
+            case 'v':
+                flags |= FLAG_v;
+                break;
+            case '?':
+                print_usage();
+                return 1;
+        }
+    }
+
+    argc -= optind;
+    argv += optind - 1;
+
+
+    if (argc == 0) {
+        print_usage();
+        return 1;
+    }
+
+    char *regexp = *++argv;
+    regex_t re;
+    regcomp(&re, regexp, REGFLAGS);
+
+    if (argc == 1) {
+        ret = grep(stdin, &re, flags);
+    } else {
+        FILE *f;
+        while (*++argv) {
+            if (**argv == '-' && *(*argv + 1) == '\0')
+                f = stdin;
+            else {
+                f = fopen(*argv, "r");
+                if (f == NULL) {
+                    fprintf(stderr, "grep: %s: %s\n", *argv, strerror(errno));
+                    ret = 1;
+                    continue;
+                }
+            }
+
+            /* grep only returns 1 or 0. */
+            ret *= grep(f, &re, flags);
+
+            if (f != stdin && fclose(f) == EOF) {
+                fprintf(stderr, "grep: %s: %s\n", *argv, strerror(errno));
+                ret = 1;
+                continue;
+            }
+        }
+    }
+
+    regfree(&re);
+    return ret;
+}