search for all string literals in an xcode project using the command line

You may use a grep command like

grep -o '"[^"\]*\(\\.[^"\]*\)*"' file > outfile

See an online demo:

s='"String1 \"here\"""String2"'grep -o '"[^"\]*\(\\.[^"\]*\)*"' <<< "$s";

The "[^"\]*\(\\.[^"\]*\)*" POSIX BRE pattern matches ", then any 0+ chars other than \ and ", then any 0+ occurrences of \ and then any char followed with any 0+ chars other than \ and " and then a " char.

If you can use a PCRE enabled grep, you may use a safer expression that will only start matching at the first unescaped double quote:

grep -oP '(?<!\\)(?:\\{2})*\K"[^"\\]*(?:\\.[^"\\]*)*"' file > outfile

Here, "[^"\\]*(?:\\.[^"\\]*)*" is the PCRE equivalent of the above POSIX BRE pattern and (?<!\\)(?:\\{2})*\K makes sure the first " is not escaped: (?<!\\) matches a location not preceded with \, then (?:\\{2})* matches 0 or more occurrences of double backslashes and then \K omits the text matched so far.

See an online demo:

s='A culprit \" escaped quote and "String1 \"here\"""String2"'grep -oP '(?<!\\)(?:\\{2})*\K"[^"\\]*(?:\\.[^"\\]*)*"' <<< "$s";

Both yield the following output:

"String1 \"here\"""String2"