The gettxt() function retrieves a text string from a message file. The arguments to the function are a message identification msgid and a default string dflt_str to be used if the retrieval fails.
The text strings are in files created by the mkmsgs utility (see mkmsgs(1)) and installed in directories in /usr/lib/locale/locale/LC_MESSAGES.
The directory locale can be viewed as the language in which the text strings are written. The user can request that messages be displayed in a specific language by setting the environment
variable LC_MESSAGES. If LC_MESSAGES is not set, the environment variable LANG will be used. If LANG is not set, the files containing the strings
are in /usr/lib/locale/C/LC_MESSAGES/*.
The user can also change the language in which the messages are displayed by invoking the setlocale(3C) function with the appropriate arguments.
If gettxt() fails to retrieve a message in a specific language it will try to retrieve the same message in U.S. English. On failure, the processing depends on what the second argument dflt_str points to. A pointer to the second argument is returned if the second argument is not the null string. If dflt_str points to the null string, a pointer to the
U.S. English text string "Message not found!!\n" is returned.
The following depicts the acceptable syntax of msgid for a call to gettxt().
<msgid> = <msgfilename>:<msgnumber>
The first field is used to indicate the file that contains the text strings and must be limited to 14 characters. These characters must be selected from the set of all character values excluding \0
(null) and the ASCII code for / (slash) and : (colon). The names of message files must be the same as the names of files created by mkmsgs and installed in /usr/lib/locale/locale/LC_MESSAGES/*. The numeric field indicates the sequence number of the string in the file. The strings
are numbered from 1 to n where n is the number of strings in the file.