XSTR(1)                              BSD                               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.  xtsr replaces these strings with references to
     this common area.  This serves to implement shared constant strings,
     which are most useful if they are also read-only.

     The command

          xstr -c name

     extracts 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 prefixed to the file.  The
     resulting C text is placed in the file x.c to be compiled.  The strings
     from this file are placed in the strings database if they are not there
     already.  Repeated strings and strings that are suffixes of existing
     strings do not cause changes to the database.

     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) saving
     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 that contains
     strings which may not, in fact, be needed.  xstr reads from its standard
     input when the dash 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        Database 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

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

SEE ALSO
     mkstr(1)