xstr(1)                                                   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 references 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 prefixed 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) 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 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:




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     xstr(1)                                                   xstr(1)



               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
          /usr/bin/xstr

          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).  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.






























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