Don't grep, but filter terminal output and colour certain lines (and print all other lines too)

Ruby:

acoc source with dependency of term-ansicolor gem.

Perl:

tail -f /some/log | perl -MTerm::ANSIColor -ne'print color("red") if /error/i; print $_; print color("reset");'

or

tail -f /some/log | perl -MTerm::ANSIColor -pne's/foo/color("cyan")."foo".color("reset")/e;'

or

tail -f /some/log | perl -MTerm::ANSIColor -pne's/(error|bar)/color("green").$1.color("reset")/eig;'

Bash:

Emacs font-lock-keywords can easily be implemented in a 3 line bash script. Call it "highlight":

    # Usage: tail -f error.log | highlight "error"
    RED="$(tput setaf 1)"
    RESET="$(tput setaf 7)"
    sed "s/$1/$RED$1$RESET/"

ssh debug3: Incorrect RSA1 identifier debug3: Could not load ".ssh/id_rsa" as a RSA1 public key

When testing ssh with -vvv, you see this in the log:

    debug3: Incorrect RSA1 identifier
    debug3: Could not load ".ssh/id_rsa" as a RSA1 public key

This is not an error.
This is not the problem you're looking for.
Your problem is something else.

(source)

See also another ssh non-error.

debug2: key_type_from_name: unknown key type '-----BEGIN'

SSH debug output can be quite misleading.
When you see the following output, it does NOT indicate a problem.

debug2: key_type_from_name: unknown key type '-----BEGIN'
debug3: key_read: missing keytype
debug3: key_read: missing whitespace
...
debug2: key_type_from_name: unknown key type '-----END'
debug3: key_read: missing keytype
debug1: identity file /home/foo/.ssh/id_rsa type 1

The final line tells you that the key was read successfully.

(source)

See also another ssh non-error.

See all commit messages in svn log

After merging a branch to trunk, subversion does not include commit logs from branches in the trunk log. With a little work it can be persuaded to display the log in a more useful way, see "svnlogg" perl script below.

When viewing this log output you may want to see the diff of one of the changes and naively type:

    svn diff -c 69271

...this may produce no output. However, if you type this intead:

    svn diff -c 69271 https://www.example.com/repo/branches/feature_xyz

...then you will see the expected output.

How to determine the branch name from the commit message is left as an exercise for the reader.


"svnlogg" perl script:

#!/usr/bin/env perl

# First, get all the commits.
# -v shows the filenames of changed files,
# -g shows commits from all merged branches.

my $LOG_TEMP = "/tmp/log.txt";

system("svn log -v -g > $LOG_TEMP");

# Then split the list into individual commits, filter out ones we don't want to see, and sort by date:

open(my $fh,"<",$LOG_TEMP) or die "cannot open file $LOG_TEMP";
local $/="------------------------------------------------------------------------"; # define the record separator
my @a = <$fh>; # populate an array with the commit messages
foreach my $aa (
    sort {
        # sort the commits by date (descending)
        my ($c) = $a =~ /\s\|\s(\d\d\d\d\-\d\d\-\d\d)\s/; # extract date field
        my ($d) = $b =~ /\s\|\s(\d\d\d\d\-\d\d\-\d\d)\s/; #
        $d cmp $c
    } @a
) {
    # exclude unwanted messages, especially the hundreds of "remove svn:mergeinfo"
    # also exclude the commit messages we use by convention in our organisation
    # to refer to branches and merges
    if ($aa !~ /(remove svn:mergeinfo|branching|final pull)/i) {
        print "$aa\n";
    }
}

Depending on your hardware it may be unusably slow, so pipe it into a file for viewing later.

Use Data::Dumper with expensive data in perl

$logger->debug(sub { "large data structure is: ".Dumper( expensive_calculation($foo) ) });

This ensures that expensive_calculation() is not performed unless the log level is DEBUG or below.

Rollback within a txn_do for DBIC

try {
    $self->schema->txn_do(sub {
        # something went bad
        die 'argh';
    });
}
catch ($e) {
    # log me
    # no roll back needed
}