Here is a collection of command-line tricks for boring, repetitive, and sometimes difficult tasks.

File tricks

show/hide hidden files

defaults write com.apple.finder AppleShowAllFiles true/false
killall Finder

Change a file’s modification date to now:

touch file

prevent .DSstore files

defaults write com.apple.desktopservices DSDontWriteNetworkStores true
killall Finder

Image manipulation

Rotate image 45 degrees clockwise

sips --rotate 45 image.jpg

Flip image horizontally or vertically

sips --flip horizontal|vertical image.jpg

Crop image to a height of 100px and a width of 150px. fit specified size.

sips --cropToHeightWidth 100 150 image.jpg

Pad image to a height of 100px and a width of 150px, use red as the padding color (default is black).

sips --padToHeightWidth 100 150 --padColor FF0000 image.jpg

Resample image to a height of 100px and a width of 150px. Image apsect ratio may be altered.

sips --resampleHeightWidth 100 150 image.jpg

Resample image to width of 300px.

sips --resampleWidth 300 image.jpg

Resample image to height of 200px.

sips --resampleHeight 200 image.jpg

Resample image so height isn’t greater than 100px and width isn’t greater than 150px.

sips --resampleHeightWidthMax 100x150 image.jpg

Text Trickery

Count number of words in the text in the Clipboard:

pbpaste | wc -w

Sort lines of text in the Clipboard and copy them back to the Clipboard:

pbpaste | sort | pbcopy

Strip duplicate lines from lines of text in the Clipboard and copy only one instance of each duplicate line back to the Clipboard (output is sorted):

pbpaste | sort | uniq | pbcopy

Find duplicate lines from lines of text in the Clipboard and copy only one instance of each duplicate line (stripping non-duplicates) back to the Clipboard (output is sorted):

pbpaste | sort | uniq -d | pbcopy

Strip duplicate lines from lines of text in the Clipboard and copy only one instance of each line (stripping duplicates entirely) back to the Clipboard (output is sorted):

pbpaste | sort | uniq -u | pbcopy

Tidy up HTML in the Clipboard and copy it back to the Clipboard:

pbpaste | tidy | pbcopy

Convert tabs to spaces for the lines in the Clipboard:

pbpaste | expand | pbcopy

Convert spaces to tabs for the lines in the Clipboard:

pbpaste | unexpand | pbcopy