setmode(3) - NetBSD Manual Pages

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SETMODE(3)              NetBSD Library Functions Manual             SETMODE(3)

getmode, setmode -- modify mode bits
Standard C Library (libc, -lc)
#include <unistd.h> void * setmode(const char *mode_str); mode_t getmode(const void *set, mode_t mode);
The setmode() function accepts a string representation of a file mode change, compiles it to binary form, and returns an abstract representa- tion 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 rep- resent 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 effects of the shell command `chmod a+x' can be dupli- cated as follows: const char *file = ""; struct stat st; mode_t newmode; stat(file, &st); newmode = getmode(setmode("a+x"), st.st_mode); chmod(file, newmode);
The setmode() function may fail and set errno for any of the errors spec- ified 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.
chmod(1), stat(2), umask(2), malloc(3)
The getmode() and setmode() functions first appeared in 4.4BSD.
Each call to 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 *. NetBSD 9.2 January 4, 2009 NetBSD 9.2
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