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bash - echo: write error: invalid argument

I am new to bash and trying to write a script that disables kworker business as in aMaia's answer here.

So far, I have this, which I run from root:

  1 #!/bin/bash                                                                      
  3 cd /sys/firmware/acpi/interrupts                                                 
  4 for i in gpe[[:digit:]]* # Don't mess with gpe_all                               
  5 do                                                                               
  6     num=`awk '{print $1}' $i`                                                    
  7     if (( $num >= 1000 )); then  # potential CPU hogs?                           
  8         # Back it up and then disable it!!                                       
  9         cp $i /root/${i}.backup                                                  
 10         echo "disable" > $i                                                      
 11     fi                                                                           
 12 done  

But running it results in:

./kkiller: line 10: echo: write error: Invalid argument

What is going on here? I thought $i was just the file name, which seems like the correct syntax for echo.

Suggestions for cleaning up/improving the script in general are also appreciated!

Update: With set -vx added to the top of the script, here is a problematic iteration:

+ for i in 'gpe[[:digit:]]*'
awk '{print $1}' $i
++ awk '{print $1}' gpe66
+ num=1024908
+ ((  1024908 >= 1000  ))
+ cp gpe66 /root/gpe66.backup
+ echo disable
./kkiller: line 10: echo: write error: Invalid argument


  1. Double-check all spelling. echo "disabled" will emit a write error even for root whereas echo "disable" succeeds.

  2. 参考答案2
  3. I had this problem too in Docker on Alpine linux environment. I think the problem is that echo by default put a newline character at the end of the string, and the kernel not accept it, but it is not the case in every system. In Docker I had this error, but the value was written despite the error message.

    The solution (in Bash): echo -n disable >/sys/firmware/acpi/interrupts/gpe66. This way no newline is echoed.

  4. 参考答案3
  5. I think it has something to with permissions. I don't think root has write access to those files by default. Try echoing manually 'disable' to that file, even as root you get the same error shown. So to make your script work, first do chmod 744 on $i before your echo, it should do the trick.