[bash] Bash에서 작은 따옴표와 큰 따옴표의 차이점

허용 대답은 중대하다. 주제를 빠르게 이해하는 데 도움이되는 표를 만들고 있습니다. 설명에는 간단한 변수 a와 색인 배열이 포함 arr됩니다.

설정하면

a=apple      # a simple variable
arr=(apple)  # an indexed array with a single element

다음 echo두 번째 열에서 표현, 우리는 세 번째 열에 표시된 결과 / 동작을 얻을 것입니다. 네 번째 열은 동작을 설명합니다.

 # | Expression  | Result      | Comments
---+-------------+-------------+--------------------------------------------------------------------
 1 | "$a"        | apple       | variables are expanded inside ""
 2 | '$a'        | $a          | variables are not expanded inside ''
 3 | "'$a'"      | 'apple'     | '' has no special meaning inside ""
 4 | '"$a"'      | "$a"        | "" is treated literally inside ''
 5 | '\''        | **invalid** | can not escape a ' within ''; use "'" or $'\'' (ANSI-C quoting)
 6 | "red$arocks"| red         | $arocks does not expand $a; use ${a}rocks to preserve $a
 7 | "redapple$" | redapple$   | $ followed by no variable name evaluates to $
 8 | '\"'        | \"          | \ has no special meaning inside ''
 9 | "\'"        | \'          | \' is interpreted inside "" but has no significance for '
10 | "\""        | "           | \" is interpreted inside ""
11 | "*"         | *           | glob does not work inside "" or ''
12 | "\t\n"      | \t\n        | \t and \n have no special meaning inside "" or ''; use ANSI-C quoting
13 | "`echo hi`" | hi          | `` and $() are evaluated inside ""
14 | '`echo hi`' | `echo hi`   | `` and $() are not evaluated inside ''
15 | '${arr[0]}' | ${arr[0]}   | array access not possible inside ''
16 | "${arr[0]}" | apple       | array access works inside ""
17 | $'$a\''     | $a'         | single quotes can be escaped inside ANSI-C quoting
18 | "$'\t'"     | $'\t'       | ANSI-C quoting is not interpreted inside ""
19 | '!cmd'      | !cmd        | history expansion character '!' is ignored inside ''
20 | "!cmd"      | cmd args    | expands to the most recent command matching "cmd"
21 | $'!cmd'     | !cmd        | history expansion character '!' is ignored inside ANSI-C quotes
---+-------------+-------------+--------------------------------------------------------------------

또한보십시오:

• ANSI-C 인용 $''-GNU Bash Manual
• 로켈 번역 $""-GNU Bash Manual
• 따옴표에 대한 3 점 공식

답변

#!/bin/sh
MYVAR=sometext
echo "double quotes gives you $MYVAR"
echo 'single quotes gives you $MYVAR'

double quotes gives you sometext
single quotes gives you $MYVAR

$ echo 'All sorts of things are ignored in single quotes, like $ & * ; |.' 

All sorts of things are ignored in single quotes, like $ & * ; |.

$ echo "Here's how we can use single ' and double \" quotes within double quotes"

Here's how we can use single ' and double " quotes within double quotes

$ echo "The current Oracle SID is $ORACLE_SID"

The current Oracle SID is test

$ today=`date '+%A, %B %d, %Y'`
$ echo $today 

Monday, September 28, 2015 

let 'foo = 2 + 1'
echo $foo
3

bar=1
let 'foo = $bar + 1'

let 'foo = '"$bar"' + 1'

(( bar=1, foo = bar + 1 ))

printf '%d\n' '$((1+1))'
-bash: printf: $((1+1)): invalid number
printf '%d\n' $((1+1))
2
printf '%d\n' "$((1+1))"
2

curl http://myurl.com --data-binary '{"requestCounter":'"$((reqcnt++))"'}'