Thread: regex in c (posix regex)

  1. #1
    Registered User
    Join Date
    Jan 2011

    regex in c (posix regex)


    I have a very simple question. How do i match a regex of :
    a) (please disregard this question )
    one or more digits

    char text[] = "x34c"
    char reg[]="x([0-9]{2})c";
    this will match my two digits after x but how to make it match all the digits between x and c given that ia don't know how many digit there are

    real number

    my regex function is as follows:

    #include <stdio.h>
    #include <sys/types.h>
    #include <string.h>
    #include <regex.h>
    #include <stdlib.h>
    #define NUM_MATCHES 4
    int regex (char *reg, char *text, int *regout){
      regex_t myreg;
      regmatch_t mymatch[NUM_MATCHES];
      int rm, i,r=0;
      char myom[1024];
      rm = regcomp (&myreg, reg, REG_EXTENDED) ; 
      rm =regexec (&myreg, text, NUM_MATCHES, mymatch, 0);
      for (i = 1; !rm && i <= myreg.re_nsub; i++){
          strncpy (myom, text + mymatch[i].rm_so, mymatch[i].rm_eo - mymatch[i].rm_so);
          myom[mymatch[i].rm_eo - mymatch[i].rm_so] = '\0';
          regout[i-1] = atoi(myom);
      regfree (&myreg);
      return r -1;
    int main (){
     int regout[2], i;
     int r;
     char text[] = "x34c"
     char reg[]="x([0-9]{2})c";
      r = regex(reg,argv[1],regout);
    	  printf("digit:%d\n",  regout[i]);

    also would this be the right (fastest) way to load a file of this type into memory:

    file example:

    51 [tab] 75
    23 [tab] 7548
    57 [tab] 78
    56 [tab] 7
    3 [tab] 711
    1 [tab] 71
    46 [tab] 78
    26 [tab] 67
    57 [tab] 45
    59 [tab] 23
    23 [tab] 72
    89 [tab] 74
    [tab] is a tab separator. I need to upload into my memory table only the type number (1 from #type:1) and the two column table (numbers). I was thinking of regex but would that be the best way to go ??
    Last edited by baxy; 11-16-2012 at 06:27 AM. Reason: stupidity, PS

  2. #2
    Registered User
    Join Date
    May 2012
    Quote Originally Posted by baxy View Post
    also would this be the right (fastest) way to load a file of this type into memory:
    Is your file as regularly formatted as your example?
    If yes, you could just loop through the file line by line using fgets() and then use sscanf() for reading the parts you want.
    while not at the end of file
        get number from first line of section (#type:xxx)
        skip two lines
        get numbers from next 6 lines
    Bye, Andreas

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