How do you append to an already existing string?

问题

I want append to a string so that every time I loop over it will add say "test" to the string.

Like in PHP you would do:

$teststr = "test1\n"
$teststr .= "test2\n"
echo = "$teststr"

echos:

test1
test2

But I need to do this in a shell script

回答1:

In classic sh, you have to do something like:

s=test1
s="${s}test2"

(there are lots of variations on that theme, like s="$s""test2")

In bash, you can use +=:

s=test1
s+=test2

回答2:

$ string="test"
$ string="${string}test2"
$ echo $string
testtest2

回答3:

#!/bin/bash
message="some text"
message="$message add some more"

echo $message

some text add some more

回答4:

teststr=$'test1\n'
teststr+=$'test2\n'
echo "$teststr"

回答5:

VAR=$VAR"$VARTOADD(STRING)"   
echo $VAR

回答6:

#!/bin/bash

msg1=${1} #First Parameter
msg2=${2} #Second Parameter

concatString=$msg1"$msg2" #Concatenated String
concatString2="$msg1$msg2"

echo $concatString 
echo $concatString2

来源：https://stackoverflow.com/questions/2250131/how-do-you-append-to-an-already-existing-string