Commands using fsck (2)

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Run a command as root, with a delay
$ sleep 1h ; sudo command or $ sudo sleep 1h ; sudo command won't work, because by the time the delay is up, sudo will want your password again.

Get the list of local files that changed since their last upload in an S3 bucket
Can be useful to granulary flush files in a CDN after they've been changed in the S3 bucket.

Mute speakers after an hour
Mutes the speakers after an hour, in case you fall asleep watching a video...

Use a var with more text only if it exists
See "Parameter Expansion" in the bash manpage. They refer to this as "Use Alternate Value", but we're including the var in the at alternative.

Binary clock
Like 7171, but fixed typo, uses fewer variables, and even more cryptic!

fdiff is a 'filtered diff'. Given a text filter and two inputs, will run the filter across the input files and diff the output.
Fdiff will run the command given by the first argument against the input files given as the second and third arguments, and diff the results. It will use 'diff' as the default diff program, but this can be changed by setting $DIFFCMD, e.g. $ export DIFFCMD=vimdiff; $ fdiff zcat 0716_0020005.raw.gz 0716_0030005.raw.gz ... This function will work under bash, but requires the use of command substitution, which is not available under a strict ANSI shell.

Send test prints to networked printer.
This will send a test print job to a networked printer.

Change the primary group of a user

Rename all .jpeg and .JPG files to .jpg

Prepare B&W scans for clean looking, searchable PDF
Scan pages in, clean them up in an image editor, save to individual files. Use this command to convert each page to PDF. Combine in Acrobat Professional, and use the built-in OCR with the "Searchable Image (Exact)" option. Gives excellent image quality and file size (avoids awful JPEG image recompression that Acrobat and other OCR systems tend to do.)


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