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.Dd December 29, 2020 .Dt LOOK 1 .Os .Sh NAME .Nm look .Nd display lines beginning with a given string .Sh SYNOPSIS .Nm .Op Fl df .Op Fl t Ar termchar .Ar string .Op Ar .Sh DESCRIPTION The .Nm utility displays any lines in .Ar file which contain .Ar string as a prefix. As .Nm performs a binary search, the lines in .Ar file must be sorted.
p If .Ar file is not specified, the file
a /usr/share/dict/words is used, only alphanumeric characters are compared and the case of alphabetic characters is ignored.
p The following options are available: l -tag -width indent t Fl d , -alphanum Dictionary character set and order, i.e., only alphanumeric characters are compared. t Fl f , -ignore-case Ignore the case of alphabetic characters. t Fl t , -terminate Ar termchar Specify a string termination character, i.e., only the characters in .Ar string up to and including the first occurrence of .Ar termchar are compared. .El .Sh ENVIRONMENT The .Ev LANG , LC_ALL and .Ev LC_CTYPE environment variables affect the execution of the .Nm utility. Their effect is described in .Xr environ 7 . .Sh FILES l -tag -width /usr/share/dict/words -compact t Pa /usr/share/dict/words the dictionary .El .Sh EXIT STATUS The .Nm utility exits 0 if one or more lines were found and displayed, 1 if no lines were found, and >1 if an error occurred. .Sh EXAMPLES Look for lines starting with .Ql xylen in the file
a /usr/share/dict/words : d -literal -offset indent $ look xylen xylene xylenol xylenyl .Ed
p Same as above, but do not consider any characters in .Ar string beyond the first .Ql e . Note that .Fl f is implicit since we are searching the default file
a /usr/share/dict/words : d -literal -offset indent $ look -t e xylen Xyleborus xylem xylene xylenol xylenyl xyletic .Ed .Sh COMPATIBILITY The original manual page stated that tabs and blank characters participated in comparisons when the .Fl d option was specified. This was incorrect and the current man page matches the historic implementation.
p The .Fl a and .Fl -alternative flags are ignored for compatibility. .Sh SEE ALSO .Xr grep 1 , .Xr sort 1 .Sh HISTORY A .Nm utility appeared in .At v7 . .Sh BUGS Lines are not compared according to the current locale's collating order. Input files must be sorted with .Ev LC_COLLATE set to .Ql C .