/usr/share/octave/4.2.2/m/strings/ is in octave-common 4.2.2-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/octave/4.2.2/m/strings/base2dec.m
/usr/share/octave/4.2.2/m/strings/bin2dec.m
/usr/share/octave/4.2.2/m/strings/blanks.m
/usr/share/octave/4.2.2/m/strings/cstrcat.m
/usr/share/octave/4.2.2/m/strings/deblank.m
/usr/share/octave/4.2.2/m/strings/dec2base.m
/usr/share/octave/4.2.2/m/strings/dec2bin.m
/usr/share/octave/4.2.2/m/strings/dec2hex.m
/usr/share/octave/4.2.2/m/strings/findstr.m
/usr/share/octave/4.2.2/m/strings/hex2dec.m
/usr/share/octave/4.2.2/m/strings/index.m
/usr/share/octave/4.2.2/m/strings/isletter.m
/usr/share/octave/4.2.2/m/strings/isstrprop.m
/usr/share/octave/4.2.2/m/strings/mat2str.m
/usr/share/octave/4.2.2/m/strings/ostrsplit.m
/usr/share/octave/4.2.2/m/strings/regexptranslate.m
/usr/share/octave/4.2.2/m/strings/rindex.m
/usr/share/octave/4.2.2/m/strings/str2num.m
/usr/share/octave/4.2.2/m/strings/strcat.m
/usr/share/octave/4.2.2/m/strings/strchr.m
/usr/share/octave/4.2.2/m/strings/strjoin.m
/usr/share/octave/4.2.2/m/strings/strjust.m
/usr/share/octave/4.2.2/m/strings/strmatch.m
/usr/share/octave/4.2.2/m/strings/strsplit.m
/usr/share/octave/4.2.2/m/strings/strtok.m
/usr/share/octave/4.2.2/m/strings/strtrim.m
/usr/share/octave/4.2.2/m/strings/strtrunc.m
/usr/share/octave/4.2.2/m/strings/substr.m
/usr/share/octave/4.2.2/m/strings/untabify.m
/usr/share/octave/4.2.2/m/strings/validatestring.m