setmode.3

早期freebsd实现

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.\"     @(#)setmode.3	8.1 (Berkeley) 6/9/93
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.Dd June 9, 1993
.Dt SETMODE 3
.Os
.Sh NAME
.Nm getmode ,
.Nm setmode
.Nd modify mode bits
.Sh SYNOPSIS
.Ft mode_t
.Fn getmode "const void *set" "mode_t mode"
.Ft void
.Fn setmode "const char *mode_str"
.Sh DESCRIPTION
The
.Fn getmode
function
returns a copy of the file permission bits
.Fa mode
as altered by the values pointed to by
.Fa set .
While only the mode bits are altered, other parts of the file mode
may be examined.
.Pp
The
.Fn setmode
function
takes an absolute (octal) or symbolic value, as described in
.Xr chmod 1 ,
as an argument
and returns a pointer to mode values to be supplied to
.Fn getmode .
Because some of the symbolic values are relative to the file
creation mask,
.Fn setmode
may call
.Xr umask 2 .
If this occurs, the file creation mask will be restored before
.Fn setmode
returns.
If the calling program changes the value of its file creation mask
after calling
.Fn setmode ,
.Fn setmode
must be called again if
.Fn getmode
is to modify future file modes correctly.
.Pp
If the mode passed to
.Fn setmode
is invalid,
.Fn setmode
returns
.Dv NULL . 
.Sh ERRORS
The
.Fn setmode
function
may fail and set errno for any of the errors specified for the library
routine
.Xr malloc 3 .
.Sh SEE ALSO
.Xr chmod 1 ,
.Xr stat 2 ,
.Xr umask 2 ,
.Xr malloc 3
.Sh HISTORY
The
.Fn getmode
and
.Fn setmode
functions first appeared in 4.4BSD.