xstr(1)

NAME

xstr - extract strings from C programs to implement shared

strings

SYNOPSIS

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

DESCRIPTION

The xstr utility maintains a file strings into which strings

in component
parts of a large program are hashed. These strings are re

placed 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

xstr

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 com

mand

xstr name

creates files x.c and xs.c as before, without using or af

fecting 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.

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' does not touch

strings

SEE ALSO

mkstr(1)

HISTORY

The xstr command appeared in 3.0BSD.

BUGS

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.

BSD December 30, 1993

BSD