Loop through a comma-separated shell variable

问题

Suppose I have a Unix shell variable as below

variable=abc,def,ghij

I want to extract all the values (abc, def and ghij) using a for loop and pass each value into a procedure.

The script should allow extracting arbitrary number of comma-separated values from $variable.

回答1:

You can use the following script to dynamically traverse through your variable, no matter how many fields it has as long as it is only comma separated.

variable=abc,def,ghij
for i in $(echo $variable | sed "s/,/ /g")
do
    # call your procedure/other scripts here below
    echo "$i"
done

Instead of the echo "$i" call above, between the do and done inside the for loop, you can invoke your procedure proc "$i".

---

Update: The above snippet works if the value of variable does not contain spaces. If you have such a requirement, please use one of the solutions that can change IFS and then parse your variable.

---

Hope this helps.

回答2:

Not messing with IFS
Not calling external command

variable=abc,def,ghij
for i in ${variable//,/ }
do
    # call your procedure/other scripts here below
    echo "$i"
done

Using bash string manipulation http://www.tldp.org/LDP/abs/html/string-manipulation.html

回答3:

If you set a different field separator, you can directly use a for loop:

IFS=","
for v in $variable
do
   # things with "$v" ...
done

You can also store the values in an array and then loop through it as indicated in How do I split a string on a delimiter in Bash?:

IFS=, read -ra values <<< "$variable"
for v in "${values[@]}"
do
   # things with "$v"
done

Test

$ variable="abc,def,ghij"
$ IFS=","
$ for v in $variable
> do
> echo "var is $v"
> done
var is abc
var is def
var is ghij

You can find a broader approach in this solution to How to iterate through a comma-separated list and execute a command for each entry.

Examples on the second approach:

$ IFS=, read -ra vals <<< "abc,def,ghij"
$ printf "%s\n" "${vals[@]}"
abc
def
ghij
$ for v in "${vals[@]}"; do echo "$v --"; done
abc --
def --
ghij --

回答4:

#/bin/bash   
TESTSTR="abc,def,ghij"

for i in $(echo $TESTSTR | tr ',' '\n')
do
echo $i
done

I prefer to use tr instead of sed, becouse sed have problems with special chars like \r \n in some cases.

other solution is to set IFS to certain separator

回答5:

Try this one.

#/bin/bash   
testpid="abc,def,ghij" 
count=`echo $testpid | grep -o ',' | wc -l` # this is not a good way
count=`expr $count + 1` 
while [ $count -gt 0 ]  ; do
     echo $testpid | cut -d ',' -f $i
     count=`expr $count - 1 `
done

回答6:

Another solution not using IFS and still preserving the spaces:

$ var="a bc,def,ghij"
$ while read line; do echo line="$line"; done < <(echo "$var" | tr ',' '\n')
line=a bc
line=def
line=ghij

回答7:

Here is an alternative tr based solution that doesn't use echo, expressed as a one-liner.

for v in $(tr ',' '\n' <<< "$var") ; do something_with "$v" ; done

It feels tidier without echo but that is just my personal preference.

回答8:

Here's my pure bash solution that doesn't change IFS, and can take in a custom regex delimiter.

loop_custom_delimited() {
    local item
    for item in $(echo $2 | sed 's/ /'`echo -e "\010"`'/g' | sed -E "s/$1/ /g"); do
        item=$(echo $item | sed 's/'`echo -e "\010"`'/ /g')
        eval "${3:-"$item"}"
    done
}
loop_custom_delimited ',' "a,b 1,b 2" 'echo $item'
echo ""
loop_custom_delimited ',' 'echo a,echo b 1,echo "b 2"'
echo ""
loop_custom_delimited ':([0-9]+)?(\.?[0-9]+):' "a:12.34:b 1:.1:b 2" 'echo "$item"'
echo ""
loop_custom_delimited ':([0-9]+)?(\.?[0-9]+):' 'echo a:1.3:echo b 1:4:echo b 2'

来源：https://stackoverflow.com/questions/27702452/loop-through-a-comma-separated-shell-variable