使用 for 循环将变量连接成由逗号分隔的单个变量

Question

I want to add the values to a variable, separated by comma, using for loop. First values should remain first and so on.

for ((i=0; i<${#MYARRAY[@]}; i++));
do
  ALL=$ALL$MYARRAY$i,
done
echo $ALL

I expect the output val1,val2,val3 but the actuel output is val1,val2,val3,

How to avoid the comma after the last value?

Answer 1

https://www.tldp.org/LDP/abs/html/string-manipulation.html is a good source. Insert the following line after the loop.

ALL=${ALL%,}

Answer 2

In this example, the first iteration does not put a comma in $ALL . In the following iteration, a comma is placed before the value. This way, there won't be any comma at the end of the output string.

MYARRAY=(val val val)
for (( i=0; i<${#MYARRAY[@]}; i++ ))
do
    if [ $i == 0 ]
    then
        ALL=$ALL$MYARRAY$i
    else
        ALL=$ALL,$MYARRAY$i
    fi
done
echo $ALL

Answer 3

This is exactly what the [*] construct is for:

myarray=(val1 val2 val3 val4)

oldIFS="$IFS"

IFS=',' 
echo "${myarray[*]}"

IFS="$oldIFS"

gives:

val1,val2,val3,val4

I am using lowercase myarray because uppercase should be reserved for system (bash) variables.

Note that "${myarray[*]}" must be inside double-quotes, otherwise you do not get the join magic. The elements are joined by the first character of IFS , which by default is a space.

Answer 4

只需在for循环后添加三个语句中的一个：

1. ALL=${ALL%,}

2. ALL=${ALL::-1}

3. ALL=${ALL%?}

Answer 5

Another option is with the translate ( tr ) command. For example:

$ myarray=(val1 val2 val3 val4)

$ echo ${myarray[*]}
val1 val2 val3 val4

$ myarray=$(echo ${myarray[*]} | tr ' ' ,)     # Replace space with ','

$ echo $myarray                                # Gives what you need
val1,val2,val3,val4