[SOLVED] Why is POSIX's libgen.h called like that?

Issue

POSIX contains a header called libgen.h (not very explicit by itself), described as

definitions for pattern matching functions

And contains the following function definitions:

char  *basename(char *);
char  *dirname(char *);

It used to contain two Regex-related functions, but they were removed in Issue 6.

Which leads me to the question: why "libgen"?

Solution

The name <libgen.h> is probably some variant of 'general library' — but history doesn't really relate.

In my printed copy of the AT&T Unix SVR4 Programmer's Reference Manual (published by Prentice-Hall in 1990 with ISBN 0-13-947029-8, but Google doesn't know much about that ISBN), there were many other functions defined in the <libgen.h> header. Section 3G "General Purpose Library Routines" listed basename() and dirname() and these other functions:

• bgets() (similar to modern getdelim())
• bufsplit()
• copylist()
• gmatch() (similar to modern fnmatch())
• isencrypt()
• mkdirp() (create directories in a path name)
• rmdirp() (remove directories in a path name)
• p2open() and p2close() (bi-directional communication with a sub-process — related to popen() and pclose())
• pathfind()
• regcmp() and regex() (regular expressions)
• strfind(), strrspn(), strtrns()
• strccpy(), strcadd(), strecpy(), streadd()

You needed to link the program with -lgen (libgen.a, libgen.so) to gain access to these functions.

Answered By - Jonathan Leffler

Answer Checked By - Candace Johnson (WPSolving Volunteer)