.Dd December 4, 2014
.Dt NL 1
.Os
.Sh NAME
.Nm nl
.Nd line numbering filter
.Sh SYNOPSIS
.Nm
.Op Fl b Ar type
.Op Fl i Ar incr
.Op Fl s Ar sep
.Op Ar file
.Sh DESCRIPTION
.Nm
reads lines from the named
.Ar file
and writes them to stdout with non-empty lines
numbered.  If no file is given
.Nm
reads from stdin.
.Sh OPTIONS
.Bl -tag -width Ds
.It Fl b Ar type
Defines which lines will be numbered:
.Bl -tag -width pstringXX
.It a
All lines.
.It n
No lines.
.It t
Only non-empty lines (default).
.It p Ns Ar expr
Only lines which match
.Ar expr ,
a regular expression as defined in
.Xr regex 7
.El
.It Fl i Ar incr
Defines the increment between numbered lines.
.It Fl s Ar sep
Defines the string used to separate line numbers and lines.  By default this is
a tab.
.El
.Sh SEE ALSO
.Xr pr 1