Finds lines in a sorted file.
The look command searches sorted files specified by the File parameter and prints all lines that begin with the string specified by the String parameter. The look command uses a binary search, therefore files specified by the File parameter must be sorted in the C locale collating sequence.
The -d and -f flags affect comparisons as in the sort command. This means a file must be sorted using the -f flag in the sort command before using the look command with the -f flag.
If the File parameter is not specified, the /usr/share/dict/words file is assumed with the collating sequence specified by the -df flags. The sort is completed using the current collating sequence. This should match the collating sequence used to produce the dictionary file. The look command limits the length of a word search to 256 characters.
| Item | Description |
|---|---|
| -d | Specifies dictionary order. Only letters, digits, tabs, and spaces are considered in comparisons. |
| -f | Compares uppercase and lowercase letters as equivalent values.
Case is not considered in the sorting so that initial-capital and
all-capital words are not grouped together at the beginning of the
output. Note: To use the look -f command, the input file must be sorted with the sort -f command. |
To search for all lines in the sortfile file that begin with the letter a, enter:
look a sortfile| Item | Description |
|---|---|
| /usr/share/dict/words | Contains the default dictionary. |