[root@rhel74 c]# cat grep2.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <regex.h>
#include <unistd.h>
static void grep_file(regex_t *re, char *path);
static void grep_stream(regex_t *re, FILE *f);
static int opt_invert = 0;
static int opt_ignorecase = 0;
int
main(int argc, char *argv[])
{
int opt;
while ((opt = getopt(argc, argv, "iv")) != -1) {
switch (opt) {
case 'i':
opt_ignorecase = 1;
break;
case 'v':
opt_invert = 1;
break;
case '?':
fprintf(stderr, "Usage: %s [-iv] [<file>...]\n", argv[0]);
exit(1);
}
}
argc -= optind;
argv += optind;
if (argc < 1) {
fputs("no pattern\n", stderr);
exit(1);
}
char *pattern = argv[0];
argc--;
argv++;
/* re は「正規表現 (Regular Expression)」の略語。
「regexp」「regex」などもよく使われます */
int re_mode = REG_EXTENDED | REG_NOSUB | REG_NEWLINE;
if (opt_ignorecase) re_mode |= REG_ICASE;
regex_t re;
int err = regcomp(&re, pattern, re_mode);
if (err != 0) {
char buf[1024];
regerror(err, &re, buf, sizeof buf);
puts(buf);
exit(1);
}
if (argc == 0) {
grep_stream(&re, stdin);
}
else {
int i;
for (i = 0; i < argc; i++) {
grep_file(&re, argv[i]);
}
}
regfree(&re);
exit(0);
}
/* path で示されるファイルを grep する */
static void
grep_file(regex_t *re, char *path)
{
FILE *f;
f = fopen(path, "r");
if (!f) {
perror(path);
exit(1);
}
grep_stream(re, f);
fclose(f);
}
static void
grep_stream(regex_t *re, FILE *f)
{
char buf[4096];
int matched;
while (fgets(buf, sizeof buf, f)) {
matched = (regexec(re, buf, 0, NULL, 0) == 0);
if (opt_invert) {
matched = !matched;
}
if (matched) {
fputs(buf, stdout);
}
}
}
[root@rhel74 c]# ./grep2 -i A test2.txt
a
[root@rhel74 c]# ./grep2 -i A -v test2.txt
b
c
d
[root@rhel74 c]# cat test2.txt
a
b
c
d
[root@rhel74 c]# cat slice.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <regex.h>
static void do_slice(regex_t *pat, FILE *f);
int
main(int argc, char *argv[])
{
regex_t pat;
int err;
int i;
if (argc < 2) {
fputs("no pattern\n", stderr);
exit(1);
}
err = regcomp(&pat, argv[1], REG_EXTENDED | REG_NEWLINE);
if (err != 0) {
char buf[1024];
regerror(err, &pat, buf, sizeof buf);
puts(buf);
exit(1);
}
if (argc == 2) {
do_slice(&pat, stdin);
}
else {
for (i = 2; i < argc; i++) {
FILE *f;
f = fopen(argv[i], "r");
if (!f) {
perror(argv[i]);
exit(1);
}
do_slice(&pat, f);
fclose(f);
}
}
regfree(&pat);
exit(0);
}
static void
do_slice(regex_t *pat, FILE *src)
{
char buf[4096];
while (fgets(buf, sizeof buf, src)) {
regmatch_t matched[1];
if (regexec(pat, buf, 1, matched, 0) == 0) {
char *str = buf + matched[0].rm_so;
regoff_t len = matched[0].rm_eo - matched[0].rm_so;
fwrite(str, len, 1, stdout);
fputc('\n', stdout);
}
}
}
[root@rhel74 c]# ./slice adm /etc/passwd
adm