NAME¶
getmode
,
setmode
—
modify mode bits
LIBRARY¶
library “libbsd”
SYNOPSIS¶
#include
<bsd/unistd.h>
void *
setmode
(
const
char *mode_str);
mode_t
getmode
(
const
void *set,
mode_t mode);
DESCRIPTION¶
The
setmode
() 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¶
The
setmode
() 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¶
The
getmode
() 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 *.