CODEWITHSUNDEEP
c
WilliamS
WilliamS

Reputation: 23

What does _("write error") mean?

In Debian 8's source code /source/procps-3.3.9/lib/fileutils.c line 38 is: char const *write_error = _("write error");

I am confused about the _("write error") part. Google showed that result on variable naming convention or library reserved names, but nothing about when _ was on the right side of = and before a () quoted string.

I also put this line into a simplest test program as only useful line then had compilation failed saying:

test.c:5:20: warning: implicit declaration of function ‘_’ [-Wimplicit-function-declaration]
    char const *str = _("test string");
                    ^

test.c:5:20: warning: initialization makes pointer from integer without a cast [-Wint-conversion]
/tmp/cczQpqTh.o: In function `main':
test.c:(.text+0x15): undefined reference to `_'
collect2: error: ld returned 1 exit status

Does anyone know what _(" ") format means?

Upvotes: 2

Views: 135

Answers (1)

unwind
unwind

Reputation: 399793

This is the standard way to mark up strings for translation using GNU gettext, a free software translation tool.

The _() macro is found by an external tool which extracts the text to make it translatable, as well as (at run-time) do look-ups to replace the literal with the necessary translation.

There is nothing special about the name _, it's just a very short but perfectly valid C identifier. Perhaps it's a bit iffy to begin a public symbol with an underscore, I'm not sure right now.

The error you're getting is because your test program very likely fails to include the <libintl.h> header (part of gettext, of course) which declares this macro. Thus you get the normal "undefined reference" error, as expected.

Upvotes: 6

Related Questions