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Full Discussion: umask question
Top Forums UNIX for Advanced & Expert Users umask question Post 302316096 by konvalo on Thursday 14th of May 2009 04:26:59 AM
Old 05-14-2009
Question

Quote:
Originally Posted by Michael Safyan
The "umask" function enables/disables the permissions that can be set for files on a per-process basis. The permissions given to open, create, mkdir, and other functions are effectively ANDed with the parameter given to the last invocation to umask, before the operation is performed. Hence, with a umask of 0, the 'group' and 'other' permissions are stripped from RWRWRW; whereas, with your second invocation of umask, you have allowed 'group' and 'other' to be conferred read and write privileges.

As for your second question, umask operates on a per-process basis. It will only affect the process in which umask is invoked (and potentially in subsequently spawned children of that process). It will not affect the processes's parent (i.e. the shell).

umask
I know when a umask of 0,the 'group' and 'other' permissions are stripped from 'RWRWRW',but I don't understand 'user' permission is still rw- ?

Thanks
 

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UMASK(2)						      BSD System Calls Manual							  UMASK(2)

NAME
umask -- set file creation mode mask SYNOPSIS
#include <sys/types.h> #include <sys/stat.h> mode_t umask(mode_t numask); DESCRIPTION
The umask() routine sets the process's file mode creation mask to numask and returns the previous value of the mask. The 9 low-order access permission bits of numask are used by system calls, including open(2), mkdir(2), mkfifo(2) and mknod(2) to turn off corresponding bits requested in file mode. (See chmod(2)). This clearing allows each user to restrict the default access to his files. The default mask value is S_IWGRP|S_IWOTH (022, write access for the owner only). Child processes inherit the mask of the calling process. RETURN VALUES
The previous value of the file mode mask is returned by the call. ERRORS
The umask() function is always successful. SEE ALSO
chmod(2), mkdir(2), mkfifo(2), mknod(2), open(2) STANDARDS
The umask() function call is expected to conform to IEEE Std 1003.1-1988 (``POSIX.1''). 4th Berkeley Distribution June 4, 1993 4th Berkeley Distribution
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