Bash Options to Fail Fast

set -o errexit  # Exit on simple commands that return non-zero status.

set -o errtrace # Makes shell functions, command substitutions, and 
                # commands in subshells inherit traps on ERR

set -o nounset  # Exit on use of unset variables.

Browse the Google Chrome SQLite Database

1. Quit Google Chrome.
2. Open SQLite Database Browser.
3. File > Open Database.
4. Browse to ~/.config/google-chrome/Default/Web Data

Change the Login Screen Power Management Preferences on Ubuntu

1. sudo chsh -s /bin/bash gdm
2. sudo passwd gdm
3. Switch User
4. Login as gdm
5. System > Preferences > Power Management
6. Edit as desired
7. Close
8. Logout
9. Login as original user
10. sudo chsh -s /bin/false gdm
11. sudo passwd -d gdm
12. sudo vipw -s
13. Replace empty password field with '*' character
14. Save the file

I used this, for example, to disable suspend on closing the lid of my laptop.

Convert a Grayscale Photo to RGB so that iPhoto will Import It v. 2

I wrote an earlier post describing how to use ImageMagick to convert a grayscale photo so that iPhoto will import it. This method is simpler. The earlier method is better if you have a large number of grayscale photos to import.

1. Open the image in Preview.
2. Tools > Match to Profile...
3. Select Color Model: RGB
4. Select ColorSync Profile: Generic RGB Profile
5. OK
6. File > Save

Convert among date formats with date(1)

http://www.gnu.org/software/coreutils/manual/html_node/date-invocation.html

# Now
$ date 
Mon Dec 14 15:09:51 EST 2009

# Relative dates
$ date -d 'yesterday'
Sun Dec 13 15:09:56 EST 2009

# Seconds since the UNIX epoch
$ date +%s
1260821405

# From seconds to the default format
$ date -d @$(date +%s)
Mon Dec 14 15:10:25 EST 2009

Delicious Bookmarklet for iPhone

Bookmark on Delicious

Return an Array from a Bash Function v. 2

I wrote an earlier post about returning an array from a Bash function. This version is better.

#! /bin/bash

# $ ./array_to_string.sh 'this' 'is a' 'test'
# declare -a output_array='([0]="this" [1]="is a" [2]="test")'
# declare -a output_array='([0]="this" [1]="is a" [2]="test")'

array_to_string()
{
    # Treat the arguments as an array:
    local -a array=( "$@" )
    declare -p array | sed -e 's/^declare -a array=//'
}

# Pass an array to a function:
input_array=( "$@" )
string="$(array_to_string "${input_array[@]}")"

# string_to_array idiom:
string_to_array_code="declare -a output_array=${string}"
eval "$string_to_array_code"

# The outputs of the following two commands should be identical:
echo "$string_to_array_code"
declare -p output_array