XSTR(1) FreeBSD General Commands Manual XSTR(1)


xstrextract strings from C programs to implement shared strings


xstr [ -cv][ -][ file ...]


The xstr utility 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 following options are available:

Read from the standard input.
Extract the strings from the C source file or the standard input ( -), 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.
Verbose mode.

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


The file xs.c 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.

The xstr utility 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. 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

The xstr utility does not touch the file strings unless new items are added, thus make(1) can avoid remaking xs.o unless truly necessary.


data base of strings
massaged C source
C source for definition of array xstr
temporary file when “ xstr name” does not touch strings




The xstr command appeared in 3.0BSD.


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.
December 30, 1993 FreeBSD