- stretch 0.8.3-1
SETMODE(3) | Library Functions Manual | SETMODE(3) |
NAME¶
getmode
, setmode
—
LIBRARY¶
library “libbsd”SYNOPSIS¶
#include <bsd/unistd.h>
void *
setmode
(const
char *mode_str);
mode_t
getmode
(const
void *set, mode_t
mode);
DESCRIPTION¶
Thesetmode
() function accepts a string representation
of a file mode change, compiles it to binary form, and returns an abstract
representation that may be passed to getmode
(). The
string may be an numeric (octal) or symbolic string of the form accepted by
chmod(1), and may represent either an exact mode to set or a
change to make to the existing mode.
The getmode
() function adjusts the file
permission bits given by mode according to the
compiled change representation set, and returns the
adjusted mode. While only the permission bits are altered, other parts of
the file mode, particularly the type, may be examined.
Because some of the possible symbolic values are defined relative
to the file creation mask, setmode
() may call
umask(2), temporarily changing the mask. If this occurs,
the file creation mask will be restored before
setmode
() returns. If the calling program changes
the value of its file creation mask after calling
setmode
(), setmode
() must be
called again to recompile the mode string if
getmode
() is to modify future file modes
correctly.
If the mode passed to setmode
() is
invalid, setmode
() returns
NULL
.
The value returned from setmode
() is
obtained from malloc
() and should be returned to the
system with free
() when the program is done with it,
generally after a call to getmode
().
EXAMPLES¶
The effects of the shell command ‘chmod a+x
myscript.sh
’ can be duplicated as follows:
const char *file = "myscript.sh"; struct stat st; mode_t newmode; stat(file, &st); newmode = getmode(setmode("a+x"), st.st_mode); chmod(file, newmode);
ERRORS¶
Thesetmode
() function may fail and set
errno for any of the errors specified for the library
routines malloc(3) or strtol(3). In
addition, setmode
() will fail and set
errno to:
- [
EINVAL
] - The mode argument does not represent a valid mode.
SEE ALSO¶
chmod(1), stat(2), umask(2), malloc(3)HISTORY¶
Thegetmode
() and setmode
()
functions first appeared in 4.4BSD.
BUGS¶
The type of set should really be some opaque struct type used only by these functions rather than void *.January 4, 2009 | Linux 4.9.0-9-amd64 |