How to 'convert' variable based on curl operation to a string in bash script

Question

I have no real experience in bash scripts but as part of a website project I am running a bash script to retrieve xml (using curl) via GETHTTP. I then want to output it to a file. But I only want to do this if the xml doesn't contain a certain string. My data supplier only permits me to perform the GETHTTP once every 6 minutes.

I am able to retrieve the xml and output to a file as follows:

$URL = "insert get http URL here"

$OUTPUT = insert filename and path here

curl -s "$URL" -o $OUTPUT

To introduce an if statement to check for the string, I have assigned the output of the curl to a variable, which I can then search:

DATA=$(curl -s "$URL")

if [[ $DATA == mystring* ]]

then $DATA -o $OUTPUT

fi

However, my big problem is that when I have tried this, each time it looks at $DATA it reruns the curl which exceeds my permitted attempts within the time period.

How do I allocate the output of the curl to a variable which can be reused without rerunning the curl each time the variable is called?

I would have thought I could just convert it to a string but my searching hasn't come up with anything so I fear I am using the wrong search terms.

arco444 · Accepted Answer · 2015-01-27 11:32:49Z

1

This should work:

URL="http://your.url/some/path"
OUTPUT="/path/to/output"
DATA=$(curl -s "$URL")

if echo $DATA | grep "mystring" >/dev/null
then
  echo $DATA > $OUTPUT
fi

$DATA is a string as long as the curl call is successful (and it returns text). You then just need to manipulate it correctly to search for your term and output it to a file.

edited Jan 27, 2015 at 11:32

answered Jan 27, 2015 at 10:47

arco444

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2 Comments

MrDave Over a year ago

Great - this works. I only need it to write the file though, not to echo the curl output in the terminal window. Is there a way of writing to $OUTPUT without actually echoing the output in the terminal?

arco444 Over a year ago

Yes, the way that's shown. What you might be seeing is the output from the grep command. Made an update to that line.

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