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version 1.24, 2003/12/21 10:02:46

version 1.25, 2003/12/21 11:18:25

Line 173 by

.An Jaromir Dolecek

.Sh NOTES

Empty string

The empty string

.Dq

cannot be matched with intuitive:

cannot be matched with the intuitive:

.Bd -literal -offset indent

expr '' : '$'

.Ed

.Pp

The reason is the returned number of matched characters (zero)

The reason is that the returned number of matched characters (zero)

is indistinguishable from failed match, so this returns failure.

is indistinguishable from a failed match, so this returns failure.

To match empty string, use something like:

To match the empty string, use something like:

.Bd -literal -offset indent

expr x'' : 'x$'

.Ed