.\" -*-nroff-*-
.TH versioncmp 3 "6 January 2007" "Straylight/Edgeware" "mLib utilities library"
.SH NAME
versioncmp \- compare Debian-format version numbers
.\" @versioncmp
.SH SYNOPSIS
.nf
.B "#include <mLib/versioncmp.h>"

.BI "int versioncmp(const char *" va ", const char *" vb ");"
.fi
.SH DESCRIPTION
The
.B versioncmp
function compares version strings.
.PP
The format of version numbers considered is
.IP
.RI [ epoch
.BR : ]
.I main
.RB [ \-
.IR sub ]
.PP
The
.I main
part may contain colons or hyphens if there is an
.I epoch
or
.IR sub ,
respectively.  Version strings are compared componentwise: first epochs,
then main parts, and finally subparts.
.PP
The component comparison is done as follows.  First, the initial
subsequence of nondigit characters is extracted from each string, and
these are compared lexicographically, using ASCII ordering, except that
letters precede non-letters.  If both are the same, an initial sequence
of digits is extracted from the remaining parts of the version strings,
and these are compared numerically (an empty sequence being considered
to have the value zero).  This process is repeated until we have a
winner or until both strings are exhausted.
.PP
The return value is 0 if the two strings are equal, \-1 if
.I va
is older than
.IR vb ,
or +1 if
.I va
is newer than
.IR vb .
.SH SEE ALSO
.BR mLib (3).
.PP
.IR "Debian Policy Manual" .
.SH AUTHOR
Mark Wooding, <mdw@distorted.org.uk>