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regex.3: Add example program 

$ gcc -Wall -Wextra -Werror -pedantic regex.c -o regex
$ ./regex.3
String = "1) John Driverhacker;
2) John Doe;
3) John Foo;
"
Matches:
#0:
offset = 25; length = 7
substring = "John Do"
#1:
offset = 38; length = 8
substring = "John Foo"

Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Alejandro Colomar 2020-10-17 15:27:49 +02:00 committed by Michael Kerrisk
parent 740656b855
commit 7e35a02866
1 changed files with 42 additions and 0 deletions
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man3/regex.3
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@ -337,6 +337,48 @@ T} Thread safety MT-Safe
.TE
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH EXAMPLES
.EX
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <regex.h>
#define ARRAY_SIZE(arr) (sizeof((arr)) / sizeof((arr)[0]))
static const char *const str =
"1) John Driverhacker;\en2) John Doe;\en3) John Foo;\en";
static const char *const re = "John.*o";
int main(void)
{
static const char *s = str;
regex_t regex;
regmatch_t pmatch[1];
regoff_t off, len;
if (regcomp(&regex, re, REG_NEWLINE))
exit(EXIT_FAILURE);
printf("String = \e"%s\e"\en", str);
printf("Matches:\en");
for (int i = 0; ; i++) {
if (regexec(&regex, s, ARRAY_SIZE(pmatch), pmatch, 0))
break;
off = pmatch[0].rm_so + (s \- str);
len = pmatch[0].rm_eo \- pmatch[0].rm_so;
printf("#%d:\en", i);
printf("offset = %jd; length = %jd\en", (intmax_t) off, (intmax_t) len);
printf("substring = \e"%.*s\e"\en", len, s + pmatch[0].rm_so);
s += pmatch[0].rm_eo;
}
exit(EXIT_SUCCESS);
}
.EE
.SH SEE ALSO
.BR grep (1),
.BR regex (7)