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