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XSTR(1)                     General Commands Manual                    XSTR(1)



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

SYNOPSIS
       xstr -c filename [ -v ] [ -l array ]
       xstr [ -l array ]
       xstr filename [ -v ] [ -l array ]

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 con-
       stant strings, which are most useful if they are also read-only.

       The command

              xstr -c filename

       extracts the strings from the C source in name, replacing string refer-
       ences  by  expressions  of  the form &&xstr[number] for some number.  An
       appropriate declaration of xstr is prepended to the file.  The  result-
       ing 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
       declaring the common xstr space called xs.c 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 filename

       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 def-
       initions yield strings or if there is conditional code  which  contains
       strings  which  may not, in fact, be needed.  xstr reads from the stan-
       dard 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(1) can avoid remaking xs.o unless truly necessary.

OPTIONS
       -c filename Take C source text from filename.

       -v          Verbose: display a progress report indicating where new  or
                   duplicate strings were found.

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

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 filename doesn't touch strings

SEE ALSO
       make(1), 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
       data base, when just placing the longer one there would do.



                                 19 April 1989                         XSTR(1)