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XSTR(1)			  BSD General Commands Manual		       XSTR(1)

NAME
     xstr -- extract strings from C programs to	implement shared strings

SYNOPSIS
     xstr [-cv]	[-] [file ...]

DESCRIPTION
     The xstr utility maintains	a file strings into which strings in component
     parts of a	large program are hashed.  These strings are replaced with
     references	to this	common area.  This serves to implement shared constant
     strings, most useful if they are also read-only.

     The following options are available:

     -	     Read from the standard input.

     -c	     Extract the strings from the C source file	or the standard	input
	     (-), replacing string references by expressions of	the form
	     (&xstr[number]) for some number.  An appropriate declaration of
	     xstr is prepended to the file.  The resulting C text is placed in
	     the file x.c, to then be compiled.	 The strings from this file
	     are placed	in the strings data base if they are not there al-
	     ready.  Repeated strings and strings which	are suffixes of	exist-
	     ing strings do not	cause changes to the data base.

     -v	     Verbose mode.

     After all components of a large program have been compiled	a file xs.c
     declaring the common xstr space can be created by a command of the	form

	   xstr

     The file xs.c should then be compiled and loaded with the rest of the
     program.  If possible, the	array can be made read-only (shared) saving
     space and swap overhead.

     The xstr utility can also be used on a single file.  A command

	   xstr	name

     creates files x.c and xs.c	as before, without using or affecting any
     strings file in the same directory.

     It	may be useful to run xstr after	the C preprocessor if any macro	defi-
     nitions yield strings or if there is conditional code which contains
     strings which may not, in fact, be	needed.	 An appropriate	command	se-
     quence for	running	xstr after the C preprocessor is:

	   cc -E name.c	| xstr -c -
	   cc -c x.c
	   mv x.o name.o

     The xstr utility does not touch the file strings unless new items are
     added, thus make(1) can avoid remaking xs.o unless	truly necessary.

FILES
     strings   data base of strings
     x.c       massaged	C source
     xs.c      C source	for definition of array	xstr
     /tmp/xs*  temporary file when "xstr name" does not	touch strings

SEE ALSO
     mkstr(1)

HISTORY
     The xstr command appeared in 3.0BSD.

BUGS
     If	a string is a suffix of	another	string in the data base, but the
     shorter string is seen first by xstr both strings will be placed in the
     data base,	when just placing the longer one there will do.

BSD			       December	30, 1993			   BSD

NAME | SYNOPSIS | DESCRIPTION | FILES | SEE ALSO | HISTORY | BUGS

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