.POT File Format

Introduction

A .pot file is the template of a GNU gettext translation: the list of every message in a program, with no translations. The letters stand for Portable Object Template. xgettext makes it by reading the program’s source code; each language’s .po catalogue is made from it.

The manual says that xgettext writes the template as domainname.po, which the maintainer renames to domainname.pot for historical reasons. A translator who starts a new language copies package.pot to LANG.po, by hand or with msginit. To bring an existing translation up to date with a newer template, msgmerge --previous merges the two: new messages arrive empty, changed ones are marked fuzzy with the earlier text kept in #| lines, and messages no longer in the template become obsolete.

The extension .pot is also used for PowerPoint templates; see the list at the end of this page.

A file dropped on any page opens in the explorer, which reads a template with the same reader as a .po file and shows the same table.

Structure

A template has exactly the syntax of a PO file: the same entries and strings, the same comments and flags and the same header entry. What sets it apart is its content:

• Every msgstr is empty, and in a plural entry so is every msgstr[N]. There is nothing translated yet.
• The header entry holds placeholders for the translator to fill in: SOME DESCRIPTIVE TITLE, YEAR and FIRST AUTHOR <EMAIL@ADDRESS>, YEAR in its comments, and values such as PACKAGE VERSION, FULL NAME <EMAIL@ADDRESS>, LANGUAGE <LL@li.org> and charset=CHARSET. A template has no translator, language or revision date yet.
• The header carries Project-Id-Version, Report-Msgid-Bugs-To and POT-Creation-Date, which xgettext fills in.
• Every entry usually has references (#:) to its place in the source, extracted comments (#.) from the programmer, and a format flag such as c-format where xgettext recognised a format string.

#. Title of the main window
#: src/main.c:57
msgid "Untitled"
msgstr ""

#: src/files.c:90
#, c-format
msgid "One file"
msgid_plural "%d files"
msgstr[0] ""
msgstr[1] ""

Because the encoding in a template is the placeholder CHARSET, a template with characters outside ASCII cannot be read as a known encoding until the placeholder is replaced; the tools treat the file as ASCII or as UTF-8, depending on how they are run.

Not described

Known, not yet covered

• Reference: how xgettext chooses what to extract from each programming language, which strings it flags and how it orders the entries. The manual describes it per language; this page does not.
• Viewer: a template is shown with the same view as a catalogue, without a view of what has still to be translated beyond the empty translation column.

Variants

• gettext PO message catalogue – the text catalogue a translator edits
• gettext POT template – the template a catalogue is made from, with every translation empty
• gettext MO binary catalogue – the compiled catalogue that programs load

Also used for

• PowerPoint 97–2003 presentation – PowerPoint’s binary presentation before PPTX: nested records in a compound file.

Links