


XSTR(1)             UNIX Programmer's Manual		  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 com-
     ponent 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, replac-
     ing 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 definitions 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 standard input when the argu-
     ment `-' is given.  An appropriate command sequence for run-
     ning _x_s_t_r after the C preprocessor is:




Printed 11/26/99	   May 7, 1986				1






XSTR(1)             UNIX Programmer's Manual		  XSTR(1)



	  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 neces-
     sary.

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.

































Printed 11/26/99	   May 7, 1986				2



