XSTR(1) 						      General Commands Manual							   XSTR(1)

NAME

       xstr - extract strings from C programs to implement shared strings

SYNOPSIS

       xstr [ -c ] [ - ] [ file ]

DESCRIPTION

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

       The command

	    xstr -c name

       will extract the strings from the C source in name, 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 already.  Repeated strings and strings which are  suffices
       of existing strings do not cause changes to the data base.

       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

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

       Xstr 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 definitions yield strings or if there is conditional code which contains
       strings which may not, in fact, be needed.  Xstr reads from its standard input when the argument `-'  is  given.   An  appropriate  command
       sequence for running xstr after the C preprocessor is:

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

       Xstr does not touch the file strings unless new items are added, thus make 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*  Temp file when `xstr name' doesn't touch strings

SEE ALSO

       mkstr(1)

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.

3rd Berkeley Distribution					    May 7, 1986 							   XSTR(1)