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.Dd December 9 2023
.Dt GRAB 1
.Os
.Sh NAME
.Nm grab
.Nd search for patterns in files
.Sh SYNOPSIS
.Nm
.Op Fl z
.Ar pattern
.Op Ar
.Nm
.Fl h
.Sh DESCRIPTION
The
.Nm
utility searches for text in files corresponding to
.Ar pattern
and prints the corresponding matches to the standard output.
Unlike the
.Xr grep 1
utility,
.Nm
is not strictly line-oriented;
instead of always matching on complete lines,
the user defines the structure of the text they would like to match and
filters on the results.
For more details on the pattern syntax, see
.Sx Pattern Syntax .
.Pp
.Nm
will read from the files provided on the command-line.
If no files are provided, the standard input will be read instead.
The special filename
.Sq -
can also be provided,
which represents the standard input.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl h , Fl Fl help
Display help information by opening this manual page.
.It Fl z , Fl Fl zero
Separate output data by null bytes
.Pq Sq \e0
instead of newlines.
This option can be used to process matches containing newlines.
.El
.Ss Pattern Syntax
A pattern is a sequences of commands optionally separated by whitespace.
A command is an operator followed by a delimiter, a regular expression,
and then terminated by the same delimiter. The last command of a pattern
need not have a terminating delimiter.
.Pp
The supported operators are as follows:
.Bl -tag -compact
.It g
Keep selections that match the given regex.
.It v
Discard selections that match the given regex.
.It x
Select everything that matches the given regex.
.It y
Select everything that doesn’t match the given regex.
.El
.Pp
An example pattern to match all numbers that contain a ‘3’ but aren’t
‘1337’ could be
.Sq x/[0-9]+/ g/3/ v/^1337$/ .
In that pattern,
.Sq x/[0-9]+/
selects all numbers in the input,
.Sq g/3/
keeps only those matches that contain the number 3,
and
.Sq v/^1337$/
filters out the specific number 1337.
.Pp
As you may use whichever delimiter you like, the following is also valid:
.Pp
.Dl x|[0-9]+| g.3. v#^1337#
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
List all your systems CPU flags, sorted and without duplicates:
.Pp
.Dl $ grab 'x/^flags.*/ x/\ew+/ v/flags/' | sort | uniq
.Sh SEE ALSO
.Xr grep 1
.Rs
.%A Rob Pike
.%D 1987
.%T Structural Regular Expressions
.%U https://doc.cat-v.org/bell_labs/structural_regexps/se.pdf
.Re
.Sh AUTHORS
.An Thomas Voss Aq Mt mail@thomasvoss.com
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