Commands using diff (109)

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Determine an image's dimensions
Simple use of ImageMagick identify function.

Execute a command on logout
Execute a command on shell logout,and run it until is finished,then shell is closed.

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 absolut path to your bash-script
Another way of doing it that's a bit clearer. I'm a fan of readable code.

Serve current directory tree at http://$HOSTNAME:8000/

list files recursively by size

Show git branches by date - useful for showing active branches
This fixes a bug found in the other scripts which fail when a branch has the same name as a file or directory in the current directory.

List all files modified by a command
Often you run a command, but afterwards you're not quite sure what it did. By adding this prefix/suffix around [COMMAND], you can list any files that were modified. . Take a nanosecond timestamp: YYYY-MM-DD HH:MM:SS.NNNNNNNNN $ date "+%F %T.%N" . Find any files that have been modified since that timestamp: $ find . -newermt "$D" . This command currently only searches below the current directory. If you want to look elsewhere change the find parameter, e.g. $ find /var/log . -newermt "$D"

directly ssh to host B that is only accessible through host A
Of course you need to be able to access host A for this ;-)


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