void
*
setmode(
const char *mode_str
)
mode_t
getmode(
const void *set
, mode_t mode
)
)
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
.
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);
)
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
]
mode
argument does not represent a valid mode.
)
and
setmode(
)
functions first appeared in
4.4BSD.
The type of
set
should really be some opaque struct type used only by these functions
rather than
void
*
.