XSTR(1)                                                                XSTR(1)



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

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

DESCRIPTION
       _X_s_t_r  maintains a file _s_t_r_i_n_g_s 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 _x_s_t_r  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 _s_t_r_i_n_g_s 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  _x_s_._c
       declaring the common _x_s_t_r space can be created by a command of the form

            xstr

       This _x_s_._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.

       _X_s_t_r can also be used on a single file.  A command

            xstr name

       creates files _x_._c and _x_s_._c as before, without using  or  affecting  any
       _s_t_r_i_n_g_s file in the same directory.

       It may be useful to run _x_s_t_r 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.  _X_s_t_r reads from its stan‐
       dard input when the argument ‘-’  is  given.   An  appropriate  command
       sequence for running _x_s_t_r after the C preprocessor is:

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

       _X_s_t_r  does  not touch the file _s_t_r_i_n_g_s unless new items are added, thus
       _m_a_k_e can avoid remaking _x_s_._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 _s_t_r_i_n_g_s

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 _x_s_t_r both strings will be placed in the
       data base, when just placing the longer one there will do.



3rd Berkeley Distribution         May 7, 1986                          XSTR(1)