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C Library Functions  - regerror (3)

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NAME

regerror(3f) - [M_regex] maps a non-zero errcode from either regcomp(3f) or regexec(3f) to a human-readable, printable message.

CONTENTS

Synopsis
Description
Options
Examples

SYNOPSIS

function regerror(this,errcode) result(errmsg)

     type(regex_type), intent(in) :: this
     integer, intent(in)          :: errcode
     character(len=:),allocatable :: errmsg

DESCRIPTION

The REGCOMP() function compiles an RE written as a string into an internal form, REGEXEC() matches that internal form against a string and reports results, REGERROR() transforms error codes from either into human-readable messages, and REGFREE() frees any dynamically-allocated storage used by the internal form of an RE.

These routines implement IEEE Std 1003.2 (POSIX.2) regular expressions (RE s); see re_format(7).

Specifically, The REGERROR(3f) function maps a non-zero errcode from either REGCOMP(3f) or REGEXEC(3f) to a human-readable, printable message. If THIS is non-NULL, the error code should have arisen from use of the regex_t pointed to by THIS, and if the error code came from REGCOMP(), it should have been the result from the most recent REGCOMP() using that regex_t.

Non-zero error codes from regcomp() and regexec() include the following:

REG_NOMATCH
	The regexec() function failed to match
REG_BADPAT
	invalid regular expression
REG_ECOLLATE
	invalid collating element
REG_ECTYPE
	invalid character class
REG_EESCAPE
	"\" applied to unescapable character
REG_ESUBREG
	invalid backreference number
REG_EBRACK
	brackets "[ ]" not balanced
REG_EPAREN
	parentheses "( )" not balanced
REG_EBRACE
	braces "{ }" not balanced
REG_BADBR
	invalid repetition count(s) in "{ }"
REG_ERANGE
	invalid character range in " [ ]"
REG_ESPACE
	ran out of memory
REG_BADRPT
	"?", "*", or "+" operand invalid
REG_EMPTY
	empty (sub)expression
REG_ASSERT
	cannot happen - you found a bug
REG_INVARG
	invalid argument, e.g. negative-length string
REG_ILLSEQ
	illegal byte sequence (bad multibyte character)

OPTIONS

THIS	a compiled regular expression from REGCOMP(3f)
ERRCODE
	the last error code generated by REGCOMP(3f) or REGEXEC(3f)
ERRMSG	the error message
ERRMSG_LEN
	size required of ERRMSG to display the entire message

EXAMPLES

Sample program

   program demo_regerror
   use M_regex, only: regex_type, regcomp, regexec, regmatch, regfree, regerror
   implicit none
   type(regex_type)             :: regex
   integer,parameter            :: maxmatch=10
   integer                      :: matches(2,maxmatch)
   integer                      :: i, istat

   character(len=:),allocatable :: input_line
   character(len=:),allocatable :: expression
   logical                      :: match

      expression= "([0-9\.\-\*\/]+)+"
      expression= "([0-9\.\-\*\/+)+"  ! intentionally bad RE (Regular Expression)
      input_line= "30*0 250*1 5 6 7"
      call regcomp(regex,expression,’x’,status=istat)
      if (istat/=0) then
        write(*,’("Regex runtime error in regcomp(3f):",a,", expression=",a)’) regerror(regex,istat),expression
        stop 1
      endif
      match=regexec(regex,input_line,matches,status=istat)
      if (istat/=0) then
        write(*,’("Regex runtime error in regexec:(3f)",a)’) regerror(regex,istat)
        stop 2
      endif
      if(match)then
         do i=1,maxmatch
            if(matches(1,i).le.0)exit
            write(*,*) ’match="’,regmatch(i,input_line,matches),’"’
         enddo
      endif
      call regfree(regex)

   end program demo_regerror

Expected output:

   Regex runtime error in regcomp(3f):brackets ([ ]) not balanced , expression=([0-9\.\-\*\/+)+
   stop 1

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Nemo Release 3.1

regerror (3)

February 23, 2025

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