Comparing variable to string in Bash

Question

I've tried the suggestion at How do I compare two string variables in an 'if' statement in Bash?

but it's not working for me.

I have

if [ "$line" == "HTTP/1.1 405 Method Not Allowed" ]
then
    <do whatever I need here>
else
    <do something else>
fi

No matter what, it always goes to else statement. I am even echoing $line ahead of this, and then copied and pasted the result, just to be sure the string was right.

Any help on why this is happening would be greatly appreciated.

test uses single = for string comparision, not double == — umläute
– umläute, Commented May 31, 2015 at 19:01
By the way, instead of echoing the line (which won't let you see invisible characters), try using the bash printf %q format to show the line as a bash string: printf %q\\n "$line" (The quotes are important.) — rici
– rici, Commented May 31, 2015 at 19:39

rici · Accepted Answer · 2015-05-31 19:33:16Z

2

If you read that line from a compliant HTTP network connection, it almost certainly has a carriage return character at the end (\x0D, often represented as \r), since the HTTP protocol uses CR-LF terminated lines.

So you'll need to remove or ignore the CR.

Here are a couple of options, if you are using bash:

Remove the CR (if present) from the line, using bash find-and-replace syntax:
```
if [ "${line//$'\r'/}" = "HTTP/1.1 405 Method Not Allowed" ]; then
```
Use a glob comparison to do a prefix match (requires [[ instead of [, but that is better anyway):
```
if [[ "$line" = "HTTP/1.1 405 Method Not Allowed"* ]]; then
```
You could use regex comparison in [[ to do a substring match, possibly with a regular expression:
```
if [[ $line =~ "Method Not Allowed" ]]; then
```
(If you use a regular expression, make sure that the regular expression operators are not quoted.)

edited May 31, 2015 at 19:33

answered May 31, 2015 at 18:30

rici

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5 Comments

bmcgonag Over a year ago

Ok, tried both of your options above, but still only get the 'else' version.

bmcgonag Over a year ago

Can I just match the 'Method Not Allowed' portion of the text somehow?

rici Over a year ago

@bmcgonag: Sure. (If you're using bash.) if [[ "$line" == *"Method Not Allowed"* ]]; then ... (But if my solutions didn't work, you might not be using bash. Please check.)

rici Over a year ago

@bmcgonag: Added a regex option, although it is also dependent on using bash.

bmcgonag Over a year ago

I used your answer along with umlauts combined. if [ "$line" = "Method Not Allowed" ]; then . thanks to you both.

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