Extracts all messages of a translation catalog that match a given
       pattern or belong to some given source files.
       Mandatory arguments to long options are mandatory for short
       options too.
   Input file location:
       INPUTFILE
              input PO file
       -D, --directory=DIRECTORY
              add DIRECTORY to list for input files search
       If no input file is given or if it is -, standard input is read.
   Output file location:
       -o, --output-file=FILE
              write output to specified file
       The results are written to standard output if no output file is
       specified or if it is -.
   Message selection:
              [-N SOURCEFILE]... [-M DOMAINNAME]...  [-J
              MSGCTXT-PATTERN] [-K MSGID-PATTERN] [-T MSGSTR-PATTERN]
              [-C COMMENT-PATTERN] [-X EXTRACTED-COMMENT-PATTERN]
       A message is selected if it comes from one of the specified
       source files, or if it comes from one of the specified domains,
       or if -J is given and its context (msgctxt) matches
       MSGCTXT-PATTERN, or if -K is given and its key (msgid or
       msgid_plural) matches MSGID-PATTERN, or if -T is given and its
       translation (msgstr) matches MSGSTR-PATTERN, or if -C is given
       and the translator's comment matches COMMENT-PATTERN, or if -X is
       given and the extracted comment matches
       EXTRACTED-COMMENT-PATTERN.
       When more than one selection criterion is specified, the set of
       selected messages is the union of the selected messages of each
       criterion.
       MSGCTXT-PATTERN or MSGID-PATTERN or MSGSTR-PATTERN or
       COMMENT-PATTERN or EXTRACTED-COMMENT-PATTERN syntax:
              [-E | -F] [-e PATTERN | -f FILE]...
       PATTERNs are basic regular expressions by default, or extended
       regular expressions if -E is given, or fixed strings if -F is
       given.
       -N, --location=SOURCEFILE
              select messages extracted from SOURCEFILE
       -M, --domain=DOMAINNAME
              select messages belonging to domain DOMAINNAME
       -J, --msgctxt
              start of patterns for the msgctxt
       -K, --msgid
              start of patterns for the msgid
       -T, --msgstr
              start of patterns for the msgstr
       -C, --comment
              start of patterns for the translator's comment
       -X, --extracted-comment
              start of patterns for the extracted comment
       -E, --extended-regexp
              PATTERN is an extended regular expression
       -F, --fixed-strings
              PATTERN is a set of newline-separated strings
       -e, --regexp=PATTERN
              use PATTERN as a regular expression
       -f, --file=FILE
              obtain PATTERN from FILE
       -i, --ignore-case
              ignore case distinctions
       -v, --invert-match
              output only the messages that do not match any selection
              criterion
   Input file syntax:
       -P, --properties-input
              input file is in Java .properties syntax
       --stringtable-input
              input file is in NeXTstep/GNUstep .strings syntax
   Output details:
       --color
              use colors and other text attributes always
       --color=WHEN
              use colors and other text attributes if WHEN.  WHEN may be
              'always', 'never', 'auto', or 'html'.
       --style=STYLEFILE
              specify CSS style rule file for --color
       --no-escape
              do not use C escapes in output (default)
       --escape
              use C escapes in output, no extended chars
       --force-po
              write PO file even if empty
       --indent
              indented output style
       --no-location
              suppress '#: filename:line' lines
       -n, --add-location
              preserve '#: filename:line' lines (default)
       --strict
              strict Uniforum output style
       -p, --properties-output
              write out a Java .properties file
       --stringtable-output
              write out a NeXTstep/GNUstep .strings file
       -w, --width=NUMBER
              set output page width
       --no-wrap
              do not break long message lines, longer than the output
              page width, into several lines
       --sort-output
              generate sorted output
       --sort-by-file
              sort output by file location
   Informative output:
       -h, --help
              display this help and exit
       -V, --version
              output version information and exit