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How can I use perl on the command-line to print only lines containing Greek unicode characters? For example, only the second of the following lines

  hullo, world
  χαῖρε, ὦ κόσμε

It should be possible to use \p{Greek} rather than the explicit range (0370-03ff, 1f00-1fff).

Methods without perl are also welcome, but I suspect sed, awk, grep cannot do this?

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You could run something along the lines of

perl -C -ne '/\p{Greek}/ and print'
1

Which encoding are you using? If it's UTF-8, you can do:

perl -CSD -ne 'print if /\p{Greek}/' input_utf8.txt >output_utf8.txt

See the -C switch in perlrun.

If it's another encoding, you can use the open pragma for more detailed control.

For example, to read and write UTF-16-LE:

perl -Mopen=':std,:encoding(UTF-16-LE)' -ne 'print if /\p{Greek}/' input_utf16le.txt >output_utf16le.txt

Or, to read a UTF-16-LE file and output in UTF-8:

perl -Mopen=':encoding(UTF-16-LE)' -CS -ne 'print if /\p{Greek}/' input_utf16le.txt >output_utf8.txt

Or, to read UTF-16-LE and write UTF-16-BE:

perl -Mopen=':std,:encoding(UTF-16-BE),IN,:encoding(UTF-16-LE)' -ne 'print if /\p{Greek}/' input_utf16le.txt >output_utf16be.txt

On these latter two, note that there is a subtle but important distinction between perl ... input.txt >output.txt and perl ... <input.txt >output.txt, since the latter reads from STDIN, while the former opens the file, so it's important to keep in mind which of the streams you're changing the encoding of.

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