1、Compound commands

Compound commands overview

Grouping

{ …; }

command grouping

( … )

command grouping in a subshell

Conditionals

[[ ... ]]

conditional expression

if …; then …; fi

conditional branching

case … esac

pattern-based branching

Loops

for word in …; do …; done

classic for-loop

for ((x=1; x<=10; x++)); do ...; done

C-style for-loop

while …; do …; done

while loop

until …; do …; done

until loop

Misc

(( ... ))

arithmetic evaluation

select word in …; do …; done

user selections

2、Expansions and substitutions

Introduction to expansions and substitutions

{A,B,C} {A..C}

Brace expansion

~/ ~root/

Tilde expansion

$FOO ${BAR%.mp3}

Parameter expansion

`command` $(command)

Command substitution

<(command) >(command)

Process substitution

$((1 + 2 + 3)) $[4 + 5 + 6]

Arithmetic expansion

Hello <---> Word!

Word splitting

/data/*-av/*.mp?

Pathname expansion

3、Builtin Commands

Declaration commands
Commands that set and query attributes/types, and manipulate simple datastructures.

Alt

Type

declare

Display or set shell variables or functions along with attributes.

typeset

builtin

export

Display or set shell variables, also giving them the export attribute.

-

special builtin

eval

A common misspelling of "evil"

-

special builtin

local

Declare variables as having function local scope.

-

builtin

readonly

Mark variables or functions as read-only.

declare -r

special builtin

unset

Unset variables and functions.

-

special builtin

shift

Shift positional parameters

-

special builtin

Control flow and data processing
Commands that operate on data and/or affect control flow.

Alt

Type

colon

"true" null command

true

special builtin

dot

Source external files

source

special builtin

false

Fail at doing nothing

-

builtin

continue / break

continue with or break out of loops.

-

special builtin

let

Arithmetic evaluation - an old fashioned way.

-

builtin

return

Break out of a function, returning the specified exit status.

-

special builtin

[

The classic test command.

test

builtin

Process and Job control
Commands related to jobs, signals, process groups, subshells.

Alt

Type

exec

Replace the shell, set redirections.

-

special builtin

exit

Exit the shell.

-

special builtin

trap

Set traps.

-

special builtin

times

Display process times.

-

special builtin

wait

Wait for background jobs and asynchronous lists.

-

builtin

I/O
Commands for reading/parsing input, or producing/formatting output of standard streams.

Alt

Type

coproc

Co-processes: Run a compound command in the background with async I/O.

-

keyword

echo

Create output from args.

-

builtin

mapfile

Create arrays from lines of input

readarray

builtin

printf

"advanced echo."

-

builtin

read

Build variables or arrays from input streams.

-

builtin

Configuration and Debugging
Commands that modify shell behavior, change special options, assist in debugging.

Alt

Type

caller

Identify/print execution frames.

-

builtin

set

Control positional parameters and shell behaviour.

-

special builtin

shopt

set/get shell options.

-

builtin

整理自： http://wiki.bash-hackers.org/start