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Convert CSV to JSON
Replace 'csv_file.csv' with your filename.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Calculate days on which Friday the 13th occurs
Simply change the years listed in the first seq, and it will print out all the months in that span of years that have Friday the 13ths in them.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Robust expansion (i.e. crash) of bash variables with a typo
By default bash expands an unbound variable to an empty string. This can be dangerous, if a critical variable name (a path prefix for example) has a typo. The -u option causes bash to treat this as an error, and the -e option causes it to exit in case of an error. These two together will make your scripts a lot safer against typos. The default behaviour can be explicitly requested using the ${NAME:-} syntax. A (less explicit) variation: #!/bin/bash -eu

Get full from half remembered commands
Show all commands having the part known by you. Eg: $apropos pdf | less

mount a cdrom

List all PostgreSQL databases. Useful when doing backups

Resize all JPEGs in a directory
This command requires the imagemagick libraries and will resize all files with the .jpg extension to a width of 1024 pixels and will keep the same proportions as the original image.

Convert text to picture
generates a picture file with the text. Some other samples in: http://www.imagemagick.org/Usage/text/


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