Share your useful shell scripts!

I've switched to fish shell on every machine I own and it's wonderful.

It has features bash can't even dream of, like closures when defining functions. Why would you ever need a closure when shell scripting, you ask?

As one example, we use Docker at $dayjob, so I sometimes connect remotely to various Docker hosts, using syntax like:

docker -H 10.10.1.1 ps

Where 10.10.1.1 can be any of a number of hosts. I made a shortcut to simplify that, using closures to define the IP:

set -g IPS 1.1 2.2 3.3
for ip in $IPS
    function d-$ip --inherit-variable ip
        docker -H 10.10.$ip $argv
    end
end

Boom, shell aliases defined programmatically, based on a loop variable.

There's much more I love about fish - the history support is another big one. If you've ever used Ctrl-R to search through your bash history, imagine that but baked deeper in. Type a partial command and hit up to start scrolling through commands in your history that contained that snippet.

A quick little password generator that I have aliased to pw:

python3.6 -c "import secrets; print(secrets.token_urlsafe(16))"

Requires the secrets module added in 3.6 that's a useful wrapper around os.urandom. 16 bytes / 128 bits of entropy, encoded using the URL-safe base64 encoding so it'll have uppercase, lowercase, and numbers. Sometimes a punctuation character, sometimes not, so if you're generating a password for a site which requires one you might need to repeat it a few times.

This is a rather old thread, but I have a few helpful bash aliases I have set up that I thought I'd share, with some annotations to explain them:

# Miscellaneous helpers.
alias stripnewline="xargs echo -n"
alias savetoclipboard="xclip -selection clipboard"
alias ssh="ssh -i ~/.ssh/my_private_key"
alias execeach="xargs -n1 -I {}"

# Login retrieval from LastPass, saves my named passwords to clipboard.
# Useful for when prompted for a password while using the command line, e.g. when doing a "git push".
alias lpassget="lpass show -cp"
alias gitpass="lpassget GitHub"
alias sshpass="lpassget SSH"

# Quickly copy my external or internal IP address to the clipboard.
# Useful for when I need to update firewall settings or other configuration details.
alias publicip="curl -s https://checkip.amazonaws.com/ | stripnewline | savetoclipboard"
alias privateip="hostname -I | stripnewline | savetoclipboard"

# General file I/O helpers.
alias grepmatch="grep -E"
alias grepinvertmatch="grep -vE"

# File safety.
alias removesymlinks="recursiveRemoveSymlinks"
alias saferm="safeRemove"

# Git tag management.
# Example, delete tags "v0.1.2" and "v0.2.0": "gitmatchingtags v0.1.2 v0.2.0 | gitremovetags"
# Example, delete all tags except those in the "v3" series and "v2.5.9": "gitnonmatchingtags v2.5.9 v3 | gitremovetags"
alias gitmatchingtags="getMatchingGitTags"
alias gitnonmatchingtags="getNonMatchingGitTags"
alias gitlocalremove="git tag --delete"
alias gitremoteremove="git push --delete origin"
alias gitremovetags="execeach bash -lic 'gitlocalremove {}; gitremoteremove {};'"

# Helper method, joins all arguments with a "|" to allow matching multiple patterns simultaneously.
constructGrepMultipleMatchPattern() {
    tagpattern="$1"
    shift 1

    for target in "$@"; do
            tagpattern="$tagpattern|$target"
    done

    echo "$tagpattern"
}

# Grabs all git tags matching any of the provided patterns.
getMatchingGitTags() {
    tagpattern=$(constructGrepMultipleMatchPattern "$@")
    git tag --list | grepmatch "$tagpattern"
}

# Grabs all git tags not matching any of the provided patterns.
getNonMatchingGitTags() {
    tagpattern=$(constructGrepMultipleMatchPattern "$@")
    git tag --list | grepinvertmatch "$tagpattern"
}

# Finds and deletes all symbolic links nested within the target directory.
# Does not allow calling without arguments to avoid inadvertently defaulting to the current directory.
recursiveRemoveSymlinks() {
    target="$1"
    if [ "$target" == "" ]; then
            echo "Missing required path argument."
    else
            find "$target" -type l -delete
    fi
}

# Removes all symbolic links in the target directories before deleting the directories themselves.
# Useful for avoiding inadvertently deleting symlinked files when trying to delete a directory.
safeRemove() {
    for target in "$@"; do
        removesymlinks "$target"
    done

    rm -rf "$@"
}

The saferm one is really useful for me in production environments where symlinks are set up inside of individual release directories and point to shared configuration files or multimedia assets. Without saferm, you have to ensure that you remove all symlinks manually before invoking rm -rf on the released git tag, which is obviously error prone. It also ensures that I don't have to unlink each symlink by hardcoding them individually inside of a script, instead finding all of them dynamically for me.

Most of these are just there to reduce the mental overhead associated with remembering what the exact commands and sequences of those commands are and the arguments and options I need to pass to them, and to reduce the amount of repetition involved in typing them out. When not a massive headache, I also like to try to make my aliases composable through piping.

I'm a fairly inexperienced shell scripter, to be honest, but I try to improve what I have over time. Even my worst scripts and aliases still make my workload a lot easier to manage :)

I run Herbstluftwm as my window manager, and like to keep the color scheme in sync with what I have defined in my Xresources file. I wrote this little nugget to pull the colors from xrdb and define local variables which can be used throughout my autostart script.

# IMPORT COLORS ---------------------------------------------------------------
xrdb -load ~/.config/Xresources
names=(black red green gold blue purple teal silver gray pink lime yellow sky magenta aqua white)
for i in {0..15}
do
     v=`xrdb -query | gawk '/*.color'"$i":'/ { print $2 }'`
     eval "${names[$i]}=$v";
done
foreground=`xrdb -query | gawk '/*.foreground/ { print $2 }'`
background=`xrdb -query | gawk '/*.background/ { print $2 }'`

There's probably a better way, but this does the job for me.

Hey, does anyone have a script that I can invoke like this?

withssh -L 8080:remote:80 <command to run locally>

I use SSH port forwarding a lot and would love a reliable script that lets me open an SSH session only for the duration of another command.

$ cat ~/bin/myip 
#!/bin/bash
curl -s https://api.ipify.org/ && echo