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convert uppercase files to lowercase files

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"

show current directory
Opens a file or URL in the user's preferred application.

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

Copy from host 1 to host 2 through your host

Both view and pipe the file without saving to disk
This is a cool trick to view the contents of the file on /dev/pts/0 (or whatever terminal you're using), and also send the contents of that file to another program by way of an unnamed pipe. All the while, you've not bothered saving any extra data to disk, like you might be tempted to do with sed or grep to filter output.

determine if a shared library is compiled as 32bit or 64bit
Determines the flavor of a shared library by looking at the addresses of its exposed functions and seeing if they are 16 bytes or 8 bytes long. The command is written so the library you are querying is passed to a variable up font -- it would be simple to convert this to a bash function or script using this format.

Use top to monitor only all processes with the same name fragment 'foo'
$ pgrep foo may return several pids for process foobar footy01 etc. like this: 11427 12576 12577 sed puts "-p " in front and we pass a list to top: $ top -p 11427 -p 12576 -p 12577

Rename files in batch

send a circular


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