I found a tome of ancient wisdom abandoned at work. Unix Power Tools from 1994 or so. Unsurprisingly I hoarded it. Very surprisingly I actually read it, cover to cover. A lot was out of date or irrelevant (I just don't care about formatting text for print). Here's the stuff I kept for later.
http://docstore.mik.ua/orelly/unix/upt/index.htm
String editing (Colon) Operators
In history substitutions there's another syntax for str sub.
$ echo /a/b/c
/a/b/c
$ echo $!:h
/a/b
That :h gives the head of the pathname.
This only works on history subs, which I don't do much of. Revisit when I get around to learning those.
History substitution
!:n* grabs the last n args from the previous command
Do-over
fc lets you fix a command. It opens the previous command in $EDITOR and then executes it.
See man bash for more
Suppressing background output
(Hi nuvolaplayer!)
Stopped jobs noising up your terminal? stty -tostop will silence them.
tpipe
tpipe is like tee but instead of writing to stdout and a file it writes to stdout and a pipe. Not sure where I'll use this (or where it appears in Ubuntu's repos...) but it seems like it'll be a lifesaver in three years when I've forgotten it.
Automatic directory setup/cleanup
Not sure how I feel about this yet. The idea seems clever so I'm holding onto it. But it also seems like a dirty hack that might turn into a trap when I've forgotten about it.
By rewriting cd as a function it can execute custom scripts upon entering or leaving a directory.
cd() {
test -r .exit.sh && sh .exit.sh
builtin cd "$1"
test -r .enter.sh && sh .enter.sh
}
Seems like a dirty hack. But the one place where I might want this is for certain git directories. My bash prompt is unwieldy. It might be less so if I could tell the git portion of my prompt not to go looking for .git directories, unless a certain shell script had said otherwise.
Still letting this one steep.
Filename wildcards
These are close enough to regexes without being exactly the same that they've always confused me.
| Wildcard | Function |
|---|---|
* |
Match 0 or more characters |
? |
Match exactly one character |
[abc] |
Match any character listed in the brackets |
[a-z] |
Match any character in range in brackets |
[!a-z] |
Match any character not in the brackets. |
{aaa,bbb,ccc} |
Match any of the comma separated words. This is shell expansion, not a wildcard, but can be used in the same way when looking for specific files |
?(abc) |
Match 0 or 1 instance of word abc |
*(abc) |
Match 0+ instances of word abc |
+(abc) |
Match 1+ instances of word abc |
!(abc) |
Match anything that doesn't contain abc |
^pat |
Match anything that doesn't match pattern, pat. Pat must contain a wildcard. |
Note that wildcards ignore dotfiles unless you explicitly match for it.
Recently changed files
alias lr='ls -lagFqt \!* | head'
Custom tests in find
find's -exec can behave as a test using the return value of the script it executes.
So if I want to find older files and ! -newer is only matching older and equally old, -exec older.sh could do the trick.
File protection
Setting the sticky bit in a directory prevents people who don't own the directory from moving files around, although they can still edit those files.
chmod 1777 for instance
Printing the unprintable
cat -v and od -c (??) can display the unprintable characters found in files.
Vim buffers
(It still surprises me I haven't learned these guys yet.)
"f uses the buffer named f.
"f4yy yanks 4 lines
"fp pastes from the buffer f
Also, you have buffers 1-9 as the last 1-9 deletions. These are filled and cycled automatically.
Vim substitution confirmation
On a substitution use /c flag to get asked abotu each sub.
Vim saving parts of files
:200,$ w newfile Writes lines 200 and up to a new file
:.,600 w newfile Writes from the current line until line 600 into a new file.
:w >> oldfile Appends to a file. Never thought to try this.
Vim multiple search
/Fungible/;/tacos/ Does one search then the other, matching fungible and then the first instance of tacos that follows.
Vim word abbreviations
:ab abbr phrase Automatically expands abbr into phrase. So...
:ab teh the Will correct all my instances of teh.
Bash pass
: is like pass in php. It does nothing but sometimes you need a nothing command. Can be used in while to loop infinitely.
Bash parameter substitution
Ever miss the ternary operator when setting up bash vars? Don't.
| Operator | Explanation |
|---|---|
${var:-default} |
Use default if var isn't set or is empty |
${var:=default} |
As above, but also sets var to default |
${var:+instead} |
If var is set and not empty, use instead. Else null. (Why?) |
${var:?message} |
Use var or die with message. |
Still not sold on :+ but the rest look great.
Debugging bash
Use #!/bin/sh -xv shows what's happening as your shell reads the script. Same as set -x?
Alas, this book is around 20 years old. Some of the stuff on it hasn't been updated. The following items looked interested but I haven't been able to get them to compile or able to find modern copies
Super LS
sls is like ls on steroids. Actually it's like ls printf with formatting.
Grabchars
read waits for enter. If you just want y/n with no enter, grabchars returns after a single keypress.
If only I could remember what script I wanted this for...
Local db
index can be used as a simple DB in your dotfiles. Not easily googleable though so I may have to skip this one.