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umask?

When would you use umask? Cant you just use chmod instead? I know umask is used to set default permissions, but I do not understand when/how it would be used. Can anyone shed some light?
Thanks

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kusuma_hs

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ASKER

ah, I see. Umask is defined globally in your unix box? It is a value, that you subtract from the default file's permissions. ie: 777-444=333 (write ane execute permissions)

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manav_mathur

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ASKER

I just checked my box, my umask is set to 022. So this means when I create new files, they will have a default permission of what?
thanks!

manav_mathur

depends on what permissions you give when you create the file. From the permission bits that you supply, the umask is deducted.

manav_mathur

for eg, if you touch a file (which gives, I believe 666 file prmissions), the actual permissions that the file gets is 644. ie -rw-r--r--

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ASKER

what are default permissions?

Say I do a cat > test.txt
garbage here
CTRL Z

ls -l is showing rw - r -r , which means default permissions were probably 666 (since my umask is 022). Am I correct?
Thanks for all the help

manav_mathur

Yes. cat, touch etc all give a default file permission of 666.

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ASKER

thanks a lot!