Wordpress - How do I add a new string to a .po or .pot file?

I am using http://wordpress.org/extend/plugins/codestyling-localization/ Give it a chance i suggest :)

Here's a shell script to generate pot files automatically. Modify the copyright, etc to fit your needs:

#!/bin/sh
#
# Author: Denis de Bernardy <http://www.mesoconcepts.com>
# Version: 0.1
# GPL licensed
#
# Created by Ryan Boren
# Later code and patches from
# Kimmo Suominen (more) and Nikolay Bachiyski (less)
# Denis de Bernardy

cwd=`pwd`

if [ -n "$1" ];
then
    cd "$1" || exit 1
    slug=`basename $1`
    dir=$cwd/$slug
else
    dir=$cwd
    slug=`basename $cwd`
fi

pot_file=$slug.pot

cp /dev/null "$dir/$pot_file"

find . -name '*.php' -print \
| sed -e 's,^\./,,' \
| sort \
| xargs xgettext \
    --keyword=__ \
    --keyword=_e \
    --keyword=_c \
    --keyword=__ngettext:1,2 \
    --keyword=_n:1,2 \
    --default-domain=$slug \
    --language=php \
    --output="$dir/$pot_file" \
    --join-existing \
    --from-code utf-8 \
    --copyright-holder='Mesoconcepts <http://www.mesoconcepts.com>' \
    --msgid-bugs-address=https://tickets.semiologic.com

# sub only the YEAR in the copyright message (the 2nd line)
sed -i '' -e '2s/YEAR/'`date +%Y`'/' "$pot_file"

# and the cherry of the pie - extract version using magic - versoextracanus!~

if [ -f $dir/style.css ];
then
    name=`fgrep -i 'Theme Name:' $dir/style.css`
    version=`fgrep -i 'Version:' $dir/style.css`
elif [ -f $dir/$slug.php ];
then
    #statements
    name=`fgrep -i 'Plugin Name:' $dir/$slug.php`
    version=`fgrep -i 'Version:' $dir/$slug.php`
else
    name=$slug
    version=
fi

name=${name##*:}
name=${name##[[:space:]]}
version=${version##*:}
version=${version##[[:space:]]}
version=${version%%[[:space:]]*}

if [ "$name" != '' ];
then
    sed -i '' -e "1s/^# SOME DESCRIPTIVE TITLE/# $name pot file/" "$pot_file"
    sed -i '' -e "s/\(^#.*\)PACKAGE\(.*\)/\1$name\2/g" "$pot_file"
fi

if [ "$version" != '' ];
then
    sed -i '' -e "s/\(Project-Id-Version: \)PACKAGE VERSION/\1$version/" "$pot_file"
fi

cd "$cwd"

Usage, assuming a *nix box (Mac or Linux):

• place the above in ~/bin/gen_pot.sh and make it executable
• make sure that ~/bin is in your $PATH
• in wp-content/themes, run gen_pot.sh yourtheme
• or from within in your theme's dir, run gen_pot.sh
• it'll output the pot file automatically...

Here's a good idea. With iCanLocalize, you can create a .po file automatically.

This generator will scan PHP file(s) and create .po files, that are used for localization. It will extract all strings wrapped in __("txt", "domain") and _e("txt", "domain") calls.

Strings can be enclosed in either double quotes (") or single quotes(') and with any character encoding.