xstr(1)                                                   xstr(1)



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

SYNOPSIS
     xstr [-] [-c] [file]

ARGUMENTS
     -    Causes xstr to read from its standard input.

     -c   Extracts the strings from the C source program into
          file, replacing string references by expressions of the
          form (&xstr [number])for some number.  An appropriate
          declaration of xstr is prefixed to file.  The resulting
          C text is placed in the file x.c, to then be compiled.
          The strings from file are placed in the strings data
          base if they are not already there.  Repeated strings
          and strings which are suffices of existing strings do
          not cause changes to the data base.

     file Specifies the name of the file that the strings will be
          extracted from.

DESCRIPTION
     xstr maintains a file called 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.

     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.

     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.











January 1992                                                    1

xstr(1)                                                   xstr(1)



EXAMPLES
     An appropriate command sequence for running xstr after the C
     preprocessor is:

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

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

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

        xstr file

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

STATUS MESSAGES AND VALUES
     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.

FILES
     /usr/bin/xstr
          Executable file
     strings
          Data base of strings
     x.c  Massaged C source file
     xs.c C source file for definition of array xstr
     /tmp/xs*
          Temporary file when ``xstr file''doesn't touch strings

SEE ALSO
     mkstr(1), strings(1)

















2                                                    January 1992