XSTR(1) BSD General Commands Manual XSTR(1)NAME
xstr — extract strings from C programs to implement shared strings
xstr [-c] [-] [file]
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, most
useful if they are also read-only.
- Xstr reads from the standard input.
-c Xstr will extract the strings from the C source file or the stan‐
dard 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.
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.
Xstr can also be used on a single file. A command
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 defi‐
nitions 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
Xstr does not touch the file strings unless new items are added, thus
make(1) can avoid remaking xs.o unless truly necessary.
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
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.
The xstr command appeared in 3.0BSD.
3rd Berkeley Distribution December 30, 1993 3rd Berkeley Distribution