exstr - extract strings from source files
exstr -e file...
exstr -r [-d] file...
The exstr utility is used to extract strings from C language source files
and replace them by calls to the message retrieval function [see
gettxt(3C)]. This utility will extract all character strings surrounded
by double quotes, not just strings used as arguments to the printf
command or the printf routine. In the first form, exstr finds all
strings in the source files and writes them on the standard output. Each
string is preceded by the source file name and a colon. The meanings of
the options are:
-e Extract a list of strings from the named C language source files,
with positional information. This list is produced on standard
output in the following format:
file the name of a C language source file
line line number in the file
position character position in the line
string the extracted text string
Normally you would redirect this output into a file. Then you
would edit this file to add the values you want to use for
msgfile and msgnum:
msgfile the file that contains the text strings that will
replace string. A file with this name must be
created and installed in the appropriate place by
the mkmsgs(1) utility.
msgnum the sequence number of the string in msgfile.
The next step is to use exstr -r to replace strings in file.
-r Replace strings in a C language source file with function calls
to the message retrieval function gettxt.
-d This option is used together with the -r option. If the message
retrieval fails when gettxt is invoked at run time, then the
extracted string is printed.
You would use the capability provided by exstr on an application program
that needs to run in an international environment and have messages print
in more than one language. exstr replaces text strings with function
calls that point at strings in a message database. The database used
depends on the runtime value of the LC_MESSAGES environment variable [see
The first step is to use exstr -e to extract a list of strings and save
it in a file. Next, examine this list and determine which strings can be
translated and subsequently retrieved by the message retrieval function.
Then, modify this file by deleting lines that can't be translated and,
for lines that can be translated, by adding the message file names and
the message numbers as the fourth (msgfile) and fifth (msgnum) entries on
a line. The message files named must have been created by mkmsgs(1) and
exist in /usr/lib/locale/locale<b>/LC_MESSAGES. The directory locale
corresponds to the language in which the text strings are written [see
setlocale(3C)]. The message numbers used must correspond to the sequence
numbers of strings in the message files.
Now use this modified file as input to exstr -r to produce a new version
of the original C language source file in which the strings have been
replaced by calls to the message retrieval function gettxt. The msgfile
and msgnum fields are used to construct the first argument to gettxt.
The second argument to gettxt is printed if the message retrieval fails
at run time. This argument is the null string, unless the -d option is
This utility cannot replace strings in all instances. For example, a
static initialized character string cannot be replaced by a function
call, or a string could be in the form of an escape sequence that cannot
be translated. In order not to break existing code, the files created by
invoking exstr -e must be examined and lines containing strings not
replaceable by function calls must be deleted. In some cases the code may
require modifications so that strings can be extracted and replaced by
calls to the message retrieval function.
The following examples show uses of exstr.
Assume that the file foo.c contains two strings:
printf("This is an example\n");
The exstr utility, invoked with the argument foo.c, extracts strings from
the named file and prints them on the standard output.
exstr foo.c produces the following output:
foo.c:This is an example\n
exstr -e foo.c > foo.stringsout produces the following output in the file
foo.c:3:8:::This is an example\n
You must edit foo.stringsout to add the values you want to use for the
msgfile and msgnum fields before these strings can be replaced by calls
to the retrieval function. If UX is the name of the message file, and
the numbers 1 and 2 represent the sequence number of the strings in the
file, here is what foo.stringsout looks like after you add this
foo.c:3:8:UX:1:This is an example\n
The exstr utility can now be invoked with the -r option to replace the
strings in the source file by calls to the message retrieval function
exstr -r foo.c <foo.stringsout >intlfoo.c produces the following output:
extern char *gettxt();
exstr -rd foo.c <foo.stringsout >intlfoo.c uses the extracted strings as
a second argument to gettxt.
extern char *gettxt();
printf(gettxt("UX:1", "This is an example\n"));
printf(gettxt("UX:2", "Hello world!\n"));
files created by mkmsgs(1)
gettxt(1), mkmsgs(1), printf(1), srchtxt(1), gettxt(3C), printf(3S),
The error messages produced by exstr are intended to be self-explanatory.
They indicate errors in the command line or format errors encountered
within the input file.
PPPPaaaaggggeeee 4444 [ Back ]