xstr -- extract strings from C programs to implement shared strings
xstr [-c] [-] [-v] [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.
-c 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.
-v 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
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.
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.
FreeBSD 5.2.1 December 30, 1993 FreeBSD 5.2.1 [ Back ]