| SETMODE(3) | Library Functions Manual | SETMODE(3) | 
getmode, setmode —
#include <unistd.h>
void *
  
  setmode(const
    char *mode_str);
mode_t
  
  getmode(const
    void *set, mode_t
    mode);
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.
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);
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]getmode() and setmode()
  functions first appeared in 4.4BSD.
setmode allocates a small amount of memory
  that there is no correct way to free.
The type of set should really be some opaque struct type used only by these functions rather than void *.
| January 4, 2009 | NetBSD 9.3 |