| .TH PCRELIMITS 3 |
| .SH NAME |
| PCRE - Perl-compatible regular expressions |
| .SH "SIZE AND OTHER LIMITATIONS" |
| .rs |
| .sp |
| There are some size limitations in PCRE but it is hoped that they will never in |
| practice be relevant. |
| .P |
| The maximum length of a compiled pattern is 65539 (sic) bytes if PCRE is |
| compiled with the default internal linkage size of 2. If you want to process |
| regular expressions that are truly enormous, you can compile PCRE with an |
| internal linkage size of 3 or 4 (see the \fBREADME\fP file in the source |
| distribution and the |
| .\" HREF |
| \fBpcrebuild\fP |
| .\" |
| documentation for details). In these cases the limit is substantially larger. |
| However, the speed of execution is slower. |
| .P |
| All values in repeating quantifiers must be less than 65536. |
| .P |
| There is no limit to the number of parenthesized subpatterns, but there can be |
| no more than 65535 capturing subpatterns. |
| .P |
| There is a limit to the number of forward references to subsequent subpatterns |
| of around 200,000. Repeated forward references with fixed upper limits, for |
| example, (?2){0,100} when subpattern number 2 is to the right, are included in |
| the count. There is no limit to the number of backward references. |
| .P |
| The maximum length of name for a named subpattern is 32 characters, and the |
| maximum number of named subpatterns is 10000. |
| .P |
| The maximum length of a subject string is the largest positive number that an |
| integer variable can hold. However, when using the traditional matching |
| function, PCRE uses recursion to handle subpatterns and indefinite repetition. |
| This means that the available stack space may limit the size of a subject |
| string that can be processed by certain patterns. For a discussion of stack |
| issues, see the |
| .\" HREF |
| \fBpcrestack\fP |
| .\" |
| documentation. |
| . |
| . |
| .SH AUTHOR |
| .rs |
| .sp |
| .nf |
| Philip Hazel |
| University Computing Service |
| Cambridge CB2 3QH, England. |
| .fi |
| . |
| . |
| .SH REVISION |
| .rs |
| .sp |
| .nf |
| Last updated: 30 November 2011 |
| Copyright (c) 1997-2011 University of Cambridge. |
| .fi |