Commands by denysonique (1)

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check the status of 'dd' in progress (OS X)
Sends SIGINFO to the process. This is a BSD feature OS X inherited. You must have the terminal window executing dd selected when entering CTRL + T for this to work.

Schedule a command while one is already running.
Useful when you have only one terminal session e.g. ssh. and want to queue up another command after the currently running has finished(in case if you forget to run that command). Originally used as ; python-updater when running emerge. When I have noticed that a package failed due to that command not run.

convert UNIX timestamp to UTC timestamp
date -ud @1320198157

generate random password (works on Mac OS X)
Prepending env LC_CTYPE=C fixes a problem with bad bytes in /dev/urandom on Mac OS X

Generate diff of first 500 lines of two files
Useful for massive files where doing a full diff would take too long. This just runs diff on the first 500 lines of each. The use of subshells to feed STDIN is quite a useful construct.

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Find writable files
Have a grudge against someone on your network? Do a "find -writable" in their directory and see what you can vandalize! But seriously, this is really useful to check the files in your own home directory to make sure they can't inadvertently be changed by someone else's wayward script.

Recall “N”th command from your BASH history without executing it.

Debug redirects between production reloads
Watches the headers of a curl, following any redirects and printing only the HTTP status and the location of the possible redirects.

Backticks are evil
This is a simple example of using proper command nesting using $() over ``. There are a number of advantages of $() over backticks. First, they can be easily nested without escapes: $ program1 $(program2 $(program3 $(program4))) versus $ program1 `program2 \`program3 \`program4\`\`` Second, they're easier to read, then trying to decipher the difference between the backtick and the singlequote: `'. The only drawback $() suffers from is lack of total portability. If your script must be portable to the archaic Bourne shell, or old versions of the C-shell or Korn shell, then backticks are appropriate, otherwise, we should all get into the habit of $(). Your future script maintainers will thank you for producing cleaner code.


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