The look command in Linux shows the lines beginning with a given string. This command also uses binary search if the file is sorted. If file is not specified, the file /usr/share/dict/words is used. And then only the alphanumeric characters are compared and the case of alphabetic characters is ignored.
look [-bdf] [-t termchar] string [file ...]
- -[string]: This option is used to search for the given string in a specified file.
look "include" Assignment.c
- -f : This option is used to ignore case of alphabetic character.
look -f ab words
- -t: This option is used to specify a string termination character, i.e., only the characters in string up to and including the first occurrence of character are compared.
look -t b abu words
- -d: This option is used to compare only alphanumeric characters.
look -d ab words
- -bd, -bf: This option uses binary search on the given word list. If you are ignoring case with -f or ignoring non-alphanumeric characters with -d, the file must be sorted in the same way.
look -bf ab words
- -h: This option is used to show the help message and exit.
- -V: This option is used to show the version information and exit.