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Re: [minor] umask 400 causes here-{doc,string} failure


From: Ilkka Virta
Subject: Re: [minor] umask 400 causes here-{doc,string} failure
Date: Sun, 11 Mar 2018 19:31:15 +0200
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:52.0) Gecko/20100101 Thunderbird/52.6.0

On 11.3. 17:17, Stephane Chazelas wrote:
$ bash -c 'umask 400; cat <<< test'
bash: cannot create temp file for here-document: Permission denied

Those shells use temporary files to store the content of the
here-documents as the Bourne shell initially did, and open them
in read-only mode to make it cat's stdin.

When umask contains the 0400 bit, the file is created without
read permission to the user, hence the error upon that second
open().
I can think of several ways to address it:

1- do nothing and blame the user
2- open the file only once for both
writing the content and making it the command's stdin
3. use a pipe instead of a temp file
4. Reset the umask temporarily to 077

One more came to mind:

5. manually chmod() the tempfile to 0400 or 0600 if the open() for reading fails with EACCES, and then retry. Should be doable with a localized change to that particular error condition, without changing the overall behaviour.

2 would have my preference.



--
Ilkka Virta / address@hidden



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