


      XSTR(1)                     (bsd 4.1)                     XSTR(1)



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

      SYNTAX
           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 references to this common area.
           This serves to implement shared constant strings, most
           useful if they are also read-only.

           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 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 suffixes 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) saving
           space and swap overhead.

           Xstr can also be used on a single file. 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 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



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      XSTR(1)                     (bsd 4.1)                     XSTR(1)



           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 date base, when just placing the
           longer one there will do.












































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