Why is this bash script not splitting the string?

Question

I'm trying to split a string with two words delimited by spaces, and this snippet isn't working for me:

$ cat > test.sh
#/bin/bash
NP="3800 480"
IFS=" "
echo $NP
echo $NP | read VAR1 VAR2
echo "Var1 : $VAR1"
echo "Var2 : $VAR2"
exit 0

And invoking it gives me:

$ chmod 755 ./test.sh && ./test.sh
3800 480
Var1 :
Var2 :

Where I was hoping to see:

3800 480
Var1 : 3800
Var2 : 480

How can a split a simple string like this in a bash script?

EDIT: (Answer I used) Thanks to the link provided by jw013, I was able to come up with this solution which worked for bash 2.04:

$ cat > test.sh
#!/bin/bash
NP="3800 480"
read VAR1 VAR2 << EOF
$NP
EOF
echo $VAR2 $VAR1

$./test.sh
480 3800

DigitalRoss · Accepted Answer · 2011-08-03 18:35:41Z

3

The problem is that the pipeline involves a fork, so you will want to make sure the rest of your script executes in the shell that does the read.

Just add ( ... ) as follows:

. . .
echo $NP | (read VAR1 VAR2
  echo "Var1 : $VAR1"
  echo "Var2 : $VAR2"
  exit 0
)

answered Aug 3, 2011 at 18:35

DigitalRoss

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3 Comments

Jamie Over a year ago

Thanks for the explanation. Point and check.

Jamie Over a year ago

But as a follow-on; how do I 'see' the variables outside the parenthesis?

DigitalRoss Over a year ago

Well, you could echo them back to the parent and capture them with command substitution. But the two scripts running after the pipeline are both near-identical copies of the original script, so why not just enclose the rest of the script in the parens? I suppose you could also call a shell procedure to execute the remaining functionality. The procedure could be defined outside the parens. (That is, outside the subshell.)

glenn jackman · Accepted Answer · 2011-08-03 19:21:57Z

3

With bash, you can use <<< (a "here string", redirect input from a string):

$ NP="3800 480"
$ read VAR1 VAR2 <<< $NP   # NB, variable is not quoted
$ echo $VAR2 $VAR1
480 3800

answered Aug 3, 2011 at 19:21

glenn jackman

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1 Comment

Jamie Over a year ago

Intriguing, but unfortunately, I'm using bash 2.04 which gives me the error syntax error near unexpected token '<<<' when used inside a script.

eckes · Accepted Answer · 2011-08-03 19:31:42Z

2

#!/bin/bash
NP="3800 480"
IFS=" "
array=($NP)
echo ${array[0]}
echo ${array[1]}

would also work

edited Aug 3, 2011 at 19:31

answered Aug 3, 2011 at 18:42

eckes

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2 Comments

DigitalRoss Over a year ago

Good, but a bash-only solution.

Daniel Haley Over a year ago

"Good, but a bash-only solution." - Which would be fine since the OP was asking for a bash solution. I'd even upvote this if eckes was invoking bash instead of bourne. ;-)

jw013 · Accepted Answer · 2011-08-04 02:04:10Z

2

Take a look at BashFAQ 024 for more about using read so that you can access the variables later.

My favorite solution (being more portable than the bash-only ones) is the here doc one:

read -r ... << EOF
$NP
EOF

answered Aug 4, 2011 at 2:04

jw013

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1 Comment

Jamie Over a year ago

Although you provided the answer I required, the answer to my main question was answered previously. Thanks again though.

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