xstr(1)                          DG/UX R4.11                         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, which are 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 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.  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:

            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   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).

NOTE
       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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