diff --git a/slides/shells/shells.md b/slides/shells/shells.md new file mode 100644 index 0000000..1bf02ce --- /dev/null +++ b/slides/shells/shells.md @@ -0,0 +1,144 @@ +# Origin + +- Used as a 'shell' around a bare-ass kernel. +- People once considered a basic shell user-friendly. +- Once worked as slow printing. + +## Use Cases + +- It's crazy-fast to write. +- Try deleting a file in Python. +- It's awful for any structured data. + +# Bangs! + +Don't say `#!/bin/bash` if you don't mean it! + +| Bang! | Apraisal | +|:------------------------|:--------------| +| `#!/bin/bash` | reasonable | +| `#!/bin/sh` | sensible | +| `#!/bin/dash` | bad idea | +| `#!/bin/zsh` | risky | +| `#!/bin/ksh` | foolish | +| `#!/usr/bin/env bash` | pathetic | +| `#!/bin/fish` | madness | +| `#!/bin/elvish` | genius | + +Protip: for a faster machine, make `sh` a link to `/bin/dash`. + +`ln -s /bin/dash /bin/dash` + +# Deviant Shells + +## `ksh` (korn shell) + +- made before `bash` +- `vi` mode by default (means you're a hacker) +- Can be posix compliant with effort + +## `elvish` + +- pure style +- built-in browser +- Ctrl+i to search for commands in $PATH +- Ctrl+n to search for command arguments +- Ctrl+l to return to previous locations + +## zsh + +- `for x in 1..10` +- great autocompletion + +# Bash Advantages + +- Equality check with "==". + * Dash cannot do `if [ $x == 3 ]; then echo y; fi` +- `$RANDOM` +- Dash cannot use `&>/dev/null` +- No history +- `$PROMPT_COMMAND` + +## Lists + +``` +myList+=(*) +echo "${myList[0]}" +``` + +# Functions + + +``` +function wotsa(){ + def="$(curl -s dict://dict.org/define:$1: | \ + grep -vP '^\d\d\d ')" + if [ "$def" = "" ]; then + echo no definition + else + echo "$def" | mdcat -p + fi +} +``` + +# Protips + +``` +"\C- ": shell-expand-line +"\C-x": glob-expand-word +``` + +- `set -e` +- `set -x` +- `set -o vi` +- Ctrl+d +- `type $whatever` +- `.inputrc` +- `PS1=foo` +- `^$` for first argument used +- `!$` for last argument used + +# Fun with Bash + +- wifi_qr.sh +- clean.sh +- theme.sh +- notflix.sh +- clip.sh +- vidget.sh + +# Zen Master Foo + +Master Foo once said to a visiting programmer: "There is more Unix-nature in one line of shell script than there is in ten thousand lines of C." + +The programmer, who was very proud of his mastery of C, said: "How can this be? +C is the language in which the very kernel of Unix is implemented!" + +Master Foo replied: "That is so. +Nevertheless, there is more Unix-nature in one line of shell script than there is in ten thousand lines of C." + +# + +The programmer grew distressed. "But through the C language we experience the enlightenment of the Patriarch Ritchie! We become as one with the operating system and the machine, reaping matchless performance!" + +Master Foo replied: "All that you say is true. +But there is still more Unix-nature in one line of shell script than there is in ten thousand lines of C." + +The programmer scoffed at Master Foo and rose to depart. +But Master Foo nodded to his student Nubi, who wrote a line of shell script on a nearby whiteboard, and said: "Master programmer, consider this pipeline. +Implemented in pure C, would it not span ten thousand lines?" + +# + +The programmer muttered through his beard, contemplating what Nubi had written. +Finally he agreed that it was so. + +"And how many hours would you require to implement and debug that C program?" asked Nubi. + +"Many," admitted the visiting programmer. "But only a fool would spend the time to do that when so many more worthy tasks await him." + +"And who better understands the Unix-nature?" Master Foo asked. "Is it he who writes the ten thousand lines, or he who, +perceiving the emptiness of the task, gains merit by not coding?" + +Upon hearing this, the programmer was enlightened. +