xstr(1) General Commands Manual xstr(1)
NAME
xstr - Extracts strings from C programs to implement shared strings
SYNOPSIS
xstr [-c] [file | -]
The xstr command maintains a file called strings into which strings in component parts of a large program are hashed.
OPTIONS
Extracts strings from the specified file.
DESCRIPTION
The strings extracted by xstr are replaced with references to this array. This serves to implement shared constant strings, most useful if
they are also read-only.
The following command extracts the strings from the C source in file, replacing string references by expressions of the form (&xstr[num-
ber]) for some number. xstr -c file
The xstr command uses file as input; the resulting C text is placed in the file x.c to then be compiled. The strings from this file are
appended to the strings file if they are not there already. Repeated strings and strings that are suffixes of existing strings do not cause
changes to the file.
If a string is a suffix of another string in the file, but the shorter string is seen first by xstr, both strings are placed in the file
strings.
After all components of a large program are compiled, a file xs.c declaring the common xstr space can be created by a command of the fol-
lowing form: xstr
Compile and load this xs.c file with the rest of the program. Some C compilers may, by default, put strings in a read-only text section.
The xstr command can also be used on a single file. The following command creates files x.c and xs.c as before, without using or affecting
a strings file in the same directory. xstr file
It may be useful to run xstr after the C preprocessor if any macro definitions yield strings or if there is conditional code that contains
strings that may not be needed. The xstr command reads from its standard input when the argument - (dash) is given. An appropriate command
sequence for running xstr after the C preprocessor is as follows: cc -E file.c | xstr -c - cc -c x.c mv x.o file.o
The xstr command does not touch the file strings unless new items are added, thus make can avoid remaking xs.o unless truly necessary.
EXAMPLES
To extract the strings from the C source in the file.c parameter, replacing string references by expressions of the form (&xstr[number]),
enter: xstr -c file
An appropriate declaration of the xstr array is prepended to file. The resulting C text is placed in the file x.c, to then be com-
piled. To declare the common xstr array space in the xs.c file, enter: xstr
FILES
File that contains the extracted strings. Modified C source. C source for definition of array xstr. Temporary file when the xstr command
does not touch strings.
SEE ALSO
Commands: mkstr(1)
xstr(1)