Fcntl

NAME

SYNOPSIS

#include <filesys.h>

LONG Fcntl( WORD fh, LONG arg, WORD cmd);

DESCRIPTION

The following commands are applicable to any file descriptor:

F_DUPFD

Return a duplicate for the file handle. The new (duplicate) handle will be an integer >= arg and < 32. If no free handles exist in that range, ENHNDL will be returned. The Fdup(fh) system call is equivalent to Fcntl(fh, 6L, F_DUPFD)

F_GETFD

Return the noinherit flag for the file descriptor. This flag is 0 if child processes started by Pexec should inherit this open file, and 1 if they should not. arg is ignored.

F_SETFD

Set the noinherit flag for the file descriptor from the low order bit of arg. The default value of the flag is 0 for handles 0-5 (the "standard" handles) and 1 for other (non-standard) handles. Note that the noinherit flag applies only to this particular file descriptor; another descriptor obtained from fh by the Fdup system call or by use of the F_DUPFD option to Fcntl will have the noinherit flag set to the default. Also note that these defaults are not the same as for the Unix operating system.

F_GETFL

Returns the user-settable file descriptor flags. These flags are the same as the mode passed to Fopen, unless they have been further modified by another Fcntl operation. arg is ignored.

F_SETFL

Set user-settable file descriptor flags from the argument arg. Only the user-settable bits in arg are considered; the settings of other bits are ignored, but should be 0 for future compatibility. Moreover, it is not possible to change a file's read-write mode or sharing modes with this call; attempts to do so will (silently) fail.

F_GETLK

arg is a pointer to an flock structure:

struct flock {
        short l_type;   /* type of lock */
#define F_RDLCK         0
#define F_WRLCK         1
#define F_UNLCK         3
        short l_whence; /* 0:file start, 1:current, 2:EOF */
        long l_start;   /* offset of locked region */
        long l_len;     /* 0 for rest of file */
        short l_pid;    /* set by F_GETLK */
};

If a lock exists which would prevent this lock from being applied to the file, the existing lock is copied into the structure and the l_pid field is set to the process id of the locking process. Otherwise, l_type is set to F_UNLCK. If a conflicting lock is held by a process on a different machine on a network, then the l_pid field will be set to a value defined by the network file system. This value will be in the range 0x1000 to 0xFFFF, and will therefore not conflict with any process id since process id's must be less than 0x1000.

F_SETLK

Set (if l_type is F_RDLCK or F_WRLCK) or clear (if l_type is F_UNLCK) an advisory lock on a file. If the file is a FIFO, the whole file must be locked or unlocked at once, i.e. l_whence, l_start, and l_len must be 0. If this lock would conflict with a lock held by another process, ELOCKED is returned. If an attempt is made to clear a non-existent lock, ENSLOCK is returned. More than one read lock may be placed on the same region of a file, but no write lock may overlap with any other sort of lock. If a process holds locks on a file, then the locks are automatically released whenever the process closes an open file handle referring to that file, or when the process terminates.

FSTAT

arg points to an XATTR structure, which is filled in with the appropriate extended file attributes for the file to which fd refers just as though the Fxattr system call (q.v.) had been made on the file.

FIONREAD

arg points to a 32 bit integer, into which is written the number of bytes that are currently available to be read from this descriptor; a read of this number of bytes or less should not cause the process to block (wait for more input). Note that for some files only an estimate can be provided, so the number is not always completely accurate.

FIONWRITE

arg points to a 32 bit integer, into which is written the number of bytes that may be written to the indicated file descriptor without causing the process to block. Note that for some files only an estimate can be provided, so the number is not always completely accurate.

The following commands are valid for any terminal device, e.g. the console or a pseudo-terminal:

TIOCGETP

Get terminal parameters. arg is a pointer to a block of memory with the following structure:

struct sgttyb {
        char sg_ispeed;         /* reserved */
        char sg_ospeed;         /* reserved */
        char sg_erase;          /* erase character */
        char sg_kill;           /* line kill character */
        short sg_flags;         /* terminal control flags */
};

TIOCSETP

Set terminal parameters from the struct sgttyb pointed to by arg.

TIOCGETC

Get terminal control characters. arg is a pointer to the following structure:

struct tchars {
        char t_intrc;   /* raises SIGINT */
        char t_quitc;   /* raises SIGQUIT */
        char t_startc;  /* starts terminal output */
        char t_stopc;   /* stops terminal output */
        char t_eofc;    /* marks end of file */
        char t_brkc;    /* marks end of line */
};

TIOCSETC

Set terminal control characters from the struct tchars pointed to by arg. Setting any character to the value 0 causes the corresponding function to become unavailable.

TIOCGLTC

Get extended terminal control characters, and put them in the structure pointed to by arg:

struct ltchars {
        char t_suspc;   /* raises SIGTSTP now */
        char t_dsuspc;  /* raises SIGTSTP when read */
        char t_rprntc;  /* redraws the input line */
        char t_flushc;  /* flushes output */
        char t_werasc;  /* erases a word */
        char t_lnextc;  /* quotes a character */
};

TIOCSLTC

Set extended terminal control characters from the struct ltchars pointed to by arg. Setting any of the characters to 0 causes the corresponding function to become unavailable.

TIOCGWINSZ

arg has type "struct winsize *". The current window size for this window is placed in the structure pointed to by arg, which has the following fields:

struct winsize {
        short   ws_row; /* # of rows of text in window*/
        short   ws_col; /* # of columns of text */
        short   ws_xpixel; /* width of window in pixels */
        short   ws_ypixel; /* height of window in pixels */
};

If any fields in the structure are 0, this means that the corresponding value is unknown.

TIOCSWINSZ

arg has type "struct winsize *". The current window size for the window is set from the structure pointed to by arg. Note that the kernel maintains the information but does not act upon it in any way; it is up to window managers to perform whatever physical changes are necessary to alter the window size, and to raise the SIGWINCH signal if necessary.

TIOCGPGRP

arg has type "long *"; the process group for the terminal is placed into the long pointed to by it.

TIOCSPGRP

arg has type "long *"; the process group for the terminal is set from the long pointed to by it. Processes in any other process group will be sent job control signals if they attempt input or output to the terminal.

TIOCSTART

Restart output to the terminal (as though the user typed control-Q) if it was stopped by a control-S or TIOCSTOP command. arg is ignored.

TIOCSTOP

Stop output to the terminal (as though the user typed control-S). arg is ignored.

TIOCGXKEY

Get the definition of a function or cursor key. arg is a pointer to a structure with the following fields:

struct xkey {
        short   xk_num;    /* function key number */
        char    xk_def[8]; /* associated string */
};

The xk_num field must be initialized with the number of the desired key:

  xk_num         Key
   0-9          F1-F10
  10-19         F11-F20 (shift F1-shift F10)
   20           cursor up
   21           cursor down
   22           cursor right
   23           cursor left
   24           help
   25           undo
   26           insert
   27           clr/home
   28           shift+cursor up
   29           shift+cursor down
   30           shift+cursor right
   31           shift+cursor left

The string currently associated with the indicated key is copied into xk_def; this string is always null-terminated.

TIOCSXKEY

arg is a structure of type struct xkey, as defined above. Both the xk_num and the xk_def fields must be defined. After execution of this command, and if the XKEY bit is set in the sg_flags field of the sgttyb structure associated with the terminal, then if the indicated key is pressed on the affected terminal, any MiNT domain process using Fread to read the key will get the string in xk_def instead of ASCII 0. Note that this translation occurs only for MiNT domain processes and only for the Fread system call. Also note that the string in xk_def must be null terminated, and so at most 7 characters may be assigned to any key.

The following commands are valid only for processes opened as files:

PBASEADDR

arg is a pointer to a 32 bit integer, into which the address of the process basepage for the process to which fh refers is written.

PPROCADDR

arg is a pointer to a 32 bit integer, into which the address of the process control structure for the process is written. Note that this control structure differs from the one found in previous versions (before 0.93) of MiNT; it no longer includes the process context, so that this part of the structure may be changed without causing compatibility problems. See the PCTXTSIZE command.

PCTXTSIZE

arg is a pointer to a 32 bit integer, into which the length of a process context structure is written. There are two of these structures located in memory just before the process control structure whose address is returned by the PPROCADDR command. The first is the current process context; the second is the saved context from the last system call.

The following commands are valid only for files which represent shared memory.

SHMSETBLK

arg is a pointer to a block of memory previously allocated by Mxalloc. The memory will be offered for sharing under the name of the file represented by fd (which must be a file in the U:\SHM subdirectory).

SHMGETBLK

arg must be 0, for future compatibility. Returns the address of the block of memory previously associated with the file via SHMSETBLK, or a NULL pointer if an error occurs. Note that different processes may see the shared memory block at different addresses in their address spaces. Therefore, the shared memory block should not contain any absolute pointers to data.

RETURNS

EIHNDL if fh is not a valid GEMDOS open handle.

EINVFN if the specified command is not valid for this file handle

Some other (LONG) negative error number if an error occurs; different commands may recognize different possible errors.  

SEE ALSO

BUGS

File locking is not yet implemented for most file systems.

Very few of the terminal control options have effect on terminals connected via serial ports or midi. In particular, it is not possible to set the baud rate, parity, flow control, or similar options with Fcntl. However, this bug will be fixed in future versions of the operating system, so programs should never modify the sg_ispeed, sg_ospeed, or sg_flags fields of the sgttyb structure, and should always use TIOCGETP to obtain the original settings of these fields before calling TIOCSETP.

Index

NAME

SYNOPSIS

DESCRIPTION

RETURNS

SEE ALSO

BUGS