[SOLVED] Matching forward slash in regex

Issue

I've troubles with preparing regex expression, matching forward slash ('/') inside.

I need to match string like "/ABC6" (forward slash, then any 3 characters, then exactly one digit). I tried expressions like "^/.{3}[0-9]", "^\/.{3}[0-9]", "^\\/.{3}[0-9]", "^\\\\/.{3}[0-9]" - without success. How should I do this?

My code:

#include <regex.h>        
regex_t regex;
int reti;

/* Compile regular expression */
reti = regcomp(&regex, "^/.{3}[0-9]", 0);
// here checking compilation result - is OK (it means: equal 0)

/* Execute regular expression */
reti = regexec(&regex, "/ABC5", 0, NULL, 0);
// reti indicates no match!

NOTE: this is about C language (gcc) on linux (Debian). And of course the expression like "^\/.{3}[0-9]" causes gcc compilation warning (unknown escape sequence).

SOLUTION: as @tripleee suggested in his answer, the problem was not caused by slash, but by brackets: '{' and '}', not allowed in BRE, but allowed in ERE. Finally I changed one line, then all works OK.

reti = regcomp(&regex, "^/.{3}[0-9]", REG_EXTENDED);

Solution

The slash is fine, the problem is that {3} is extended regular expression (ERE) syntax -- you need to pass REG_EXTENDED or use \{3\} instead (where of course in a C string those backslashes need to be doubled).

Answered By - tripleee

Answer Checked By - Clifford M. (WPSolving Volunteer)