.TH LOOK 1
.SH NAME
look \- find lines in a sorted list
.SH SYNOPSIS
.B look
[
.BI -dfnixt c
]
[
.I string
]
[
.I file
]
.SH DESCRIPTION
.I Look
consults a sorted
.I file
and prints all lines that begin with
.IR string .
It uses binary search.
.PP
The following options are recognized.
Options
.B dfnt
affect comparisons as in
.IR  sort (1).
.TP
.B -i
Interactive.
There is no
.I string
argument; instead
.I look
takes lines from the standard input as strings to be looked up.
.TP
.B -x
Exact.
Print only lines of the file whose key matches
.I string
exactly.
.TP
.B  -d
`Directory' order:
only letters, digits,
tabs and blanks participate in comparisons.
.TP
.B  -f
Fold.
Upper case letters compare equal to lower case.
.TP
.B -n
Numeric comparison with initial string of digits, optional minus sign,
and optional decimal point.
.TP
.BR -t [ \f2c\f1 ]
Character
.I c
terminates the sort key in the
.IR file .
By default, tab terminates the key.  If
.I c
is missing the entire line comprises the key.
.PP
If no
.I file
is specified,
.B /lib/words
is assumed, with collating sequence
.BR df .
.SH FILES
.B /lib/words
.SH SOURCE
.B /sys/src/cmd/look.c
.SH "SEE ALSO"
.IR sort (1), 
.IR grep (1)
.SH DIAGNOSTICS
The exit status is
.RB `` "not found" ''
if no match is found, and
.RB `` "no dictionary" ''
if
.I file
or the default dictionary cannot be opened.