XSTR(1)                 System General Commands Manual                 XSTR(1)

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

SYNOPSIS
     xstr [-cv] [-l array] [-o xname] [-O xsname] [-] [file ...]

DESCRIPTION
     xstr 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 options are as follows:

     -           Cause xstr to read from the standard input.

     -c          xstr will extract the strings from the C source file or the
                 standard input (-), replacing string references by expres-
                 sions of the form (&xstr[number]) for some number.  An appro-
                 priate declaration of xstr is prepended to the file.  The
                 resulting C text is placed in the file x.c, to then be com-
                 piled.  The strings from this file are placed in the strings
                 database if they are not there already.  Repeated strings and
                 strings which are suffixes of existing strings do not cause
                 changes to the database.

     -l array    Specify the named array in program references to abstracted
                 strings.  The default array name is ``xstr''.

     -v          Be verbose.

     -o xname    Override the default filename of x.c to xname.  It is assumed
                 that the user will make a wise filename choice.

     -O xsname   Override the default filename of xs.c to xsname.  It is
                 assumed that the user will make a wise filename choice.

     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.

     xstr can also be used on a single file.  The following command creates
     files x.c and xs.c as before, without using or affecting any strings file
     in the same directory:

           $ xstr name

     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
     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, so that
     make(1) 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*    temporary file when ``xstr name'' doesn't 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 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.

BSD                           September 14, 2004                           BSD