R (Chandra) Chandrasekhar wrote:
Dear Folks,
Hello,
I want to comment out certain lines in a file that match a particular
pattern. The file contains lines with characters like: {, }, ==, and ".
'{' is only special in a regular expression if it is immediately
followed by a numerical digit, for example '{7}' is special whereas
'{abc}' is not. '}' is not special unless it is part of '{<numerical
digits>}'. '=' and '"' are never special in a regular expression.
Specifically, I want to replace lines beginning with
ATTRS{idVendor}=="07b4", ATTRS{idProduct}=="0109",
There is nothing in that that needs to be escaped.
with
# ATTRS{idVendor}=="07b4", ATTRS{idProduct}=="0109",
I have been unsuccessful in including the pattern as above and have had
to work around using just the two number patterns like so:
--------
#!/usr/bin/perl -i.bak -pl
use warnings;
use strict;
m/07b4/ and m/0109/ and s/$_/# $_/;
Use s/^/# /; instead of s/$_/# $_/;.
--------
This works, but leaves me wondering how I could include the full
pattern, including metacharacters. Using \Q did not help, but perhaps I
was doing something wrong.
I have included some sample lines that can be used as an input file.
--------
ATTRS{idVendor}=="0553", ATTRS{idProduct}=="0202", MODE="0660",
GROUP="plugdev"
$ perl -Mre=debug -wle'my $x = qr/ATTRS{idVendor}=="0553",
ATTRS{idProduct}=="0202", MODE="0660", GROUP="plugdev"/'
Freeing REx: `","'
Compiling REx `ATTRS{idVendor}=="0553", ATTRS{idProduct}=="0202",
MODE="0660", GROUP="plugdev"'
size 22 Got 180 bytes for offset annotations.
first at 1
1: EXACT <ATTRS{idVendor}=="0553", ATTRS{idProduct}=="0202",
MODE="066...>(22)
22: END(0)
anchored "ATTRS{idVendor}=="0553", ATTRS{idProduct}=="0202",
MODE="0660", GROUP="plugdev"" at 0 (checking anchored isall) minlen 79
Offsets: [22]
1[79] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0]
0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 0[0] 80[0]
Freeing REx: `"ATTRS{idVendor}==\"0553\", ATTRS{idProduct}==\"0202\",
MODE"......'
Nope, nothing in there that needs to be escaped.
John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall
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