22

This is the shell code I am running:

#!bin/bash

while true
do
        req=$(curl http://localhost/devcalls/camerarequest.php)

        if [ "$req" == "1" ]
        then
                sudo bash /home/ckoy-admin/HAS_system/camera/cam.sh
        fi
done

and this is the error I get when I execute:

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100     1  100     1    0     0     56      0 --:--:-- --:--:-- --:--:--    58
CAM.sh: 7: [: 1: unexpected operator

Please let me know what is wrong here.

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6
  • 1
    All I can think of is that there might be some invisible characters in your file. Did you type that in with vi? Commented Jun 17, 2017 at 12:44
  • 2
    How do you run the script? Commented Jun 17, 2017 at 12:44
  • 1
    Show content of echo "$req" | hexdump -C. Check your file for special characters with cat -A file or cat -v file. Commented Jun 17, 2017 at 12:52
  • 7
    You are running your script with sh CAM.sh, and sh is a shell (probably dash) that doesn't recognize == as a valid operator with the [ command. Commented Jun 17, 2017 at 12:54
  • 1
    @chepner.. yes, changing the == to -eq worked! Commented Jun 18, 2017 at 5:37

5 Answers 5

Reset to default
28 
if [ "$req" = 1 ]

or even better

if [ "$req" -eq 1 ]

See the syntax and operators in man test.

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3 Comments

@phd..Adding the -eq instead of == worked.. Thank you.. :D
same for me, also had to put -ne instead of !=
If the script were actually executed by Bash, it would actually work; but the shebang is broken, so the script will have been executed by sh after all, which does not portably accept == in lieu of the correct and portable =. For the record, for the shebang to be valid, it needs to start with exactly the two bytes #! followed by the absolute path to the desired interpreter (i.e. /bin/bash, not just bin/bash).
20

To compare INTEGER

if [ "$req" -eq 1 ]

To compare STRING

if [ "$req" = "string" ]
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Comments

2

using bash run.sh instead of sh run.sh worked for me.

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Comments

1

View shell:

$ ls -l /bin/sh
lrwxrwxrwx 1 root root 4 Aug 11 2021 /bin/sh -> dash

This problem occurs due to the incompatibility between dash and bash. There are two ways to solve it:

  (1): sudo dpkg-reconfigure dash select NO
Change the dash of ubuntu's default shell link to traditional bash
lrwxrwxrwx 1 root root 4 August 11 09:53 /bin/sh -> dash (before modification)
lrwxrwxrwx 1 root root 4 Aug 11 09:53 /bin/sh -> bash
This problem occurs due to the incompatibility between dash and bash. .

  (2): Change == to =: because the default judgment statement in dash is =. .
For specific dash and bash, you can use man to find out. .
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-1

if [ "expr n%2 -eq 0" ]

if [ "expr n%2=0" ]

or

if [ 'expr n%2=0' ]

if [ 'expr n%2 -eq 0' ]

you can use any 4 method above mentioned i have tried all other answers but including every thing inside the "" gave me the output

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1 Comment

This is complete hallucination. The quotes turn this into a check for a non-empty string, which is true by definition.

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