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Reload this Page what does "cat > /sbin/reboot <<EOF" do in init script?
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Old 01-07-2021, 08:06 AM   #1
flyxtop
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Registered: Apr 2013
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what does "cat > /sbin/reboot <<EOF" do in init script?

this is the init script from a ramdisk image.
After kernel finishes booting, it executes this init script.
--------------------------
/bin/busybox --install -s

rm /sbin/reboot
cat > /sbin/reboot <<EOF
#/bin/sh

exec /bin/busybox reboot -f
EOF
-------------------

I think when this script is run, the initrd has been already mounted. What does "cat > /sbin/reboot <<EOF" do?
 
Old 01-07-2021, 08:15 AM   #2
Guttorm
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Hi

It writes the content until the next EOF to the /sbin/reboot file - first it removes the file, then replaces it with this:
Code:
#/bin/sh

exec /bin/busybox reboot -f
 
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Old 01-07-2021, 08:25 AM   #3
flyxtop
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Thumbs up that clearly explained it to me.
Quote:
Originally Posted by Guttorm View Post
Hi

It writes the content until the next EOF to the /sbin/reboot file - first it removes the file, then replaces it with this:
Code:
#/bin/sh

exec /bin/busybox reboot -f
Ah, that was so. Thank you! (BTW, I didn't know LQ requires Title for a reply)
 
Old 01-07-2021, 09:30 AM   #4
Turbocapitalist
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The name for that method of creating output is called a here document.

The name for the method of getting the here document, or other output, into a file is called redirection.

It can either overwrite or append.
 
  


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