.TH Fcntl 2 "MiNT Programmer's Manual" "Version 1.08" "Aug. 5, 1993" .SH NAME Fcntl \- perform various control operations on a file .SH SYNOPSIS .nf #include LONG Fcntl( WORD fh, LONG arg, WORD cmd); .fi .SH DESCRIPTION .I Fcntl performs various control operations on the open file with GEMDOS file handle .IR fh . The specific command to perform is given by .IR cmd ; the possible commands are given by symbolic constants in filesys.h, and are listed below. .I arg is an argument whose meaning depends on the command. .PP The following commands are applicable to any file descriptor: .IP 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 .IR Fdup ( fh ) system call is equivalent to .IR Fcntl ( fh , 6L, F_DUPFD) .IP F_GETFD Return the noinherit flag for the file descriptor. This flag is 0 if child processes started by .I Pexec should inherit this open file, and 1 if they should not. .I arg is ignored. .IP F_SETFD Set the noinherit flag for the file descriptor from the low order bit of .IR 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 .I fh by the .I Fdup system call or by use of the F_DUPFD option to .I 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. .IP F_GETFL Returns the user-settable file descriptor flags. These flags are the same as the mode passed to .IR Fopen , unless they have been further modified by another .I Fcntl operation. .I arg is ignored. .IP F_SETFL Set user-settable file descriptor flags from the argument .IR arg . Only the user-settable bits in .I 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. .IP F_GETLK .I arg is a pointer to an flock structure: .nf 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 */ }; .fi 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. .IP 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. .IP F_SETLKW Like .IR F_SETLK , but if the lock requested would conflict with a lock held by another process, the calling process is suspended until all conflicting locks are released. .IP FSTAT .I arg points to an XATTR structure, which is filled in with the appropriate extended file attributes for the file to which .I fd refers just as though the .I Fxattr system call (q.v.) had been made on the file. .IP FIONREAD .I 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. .IP FIONWRITE .I 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. .PP The following commands are valid for any terminal device, e.g. the console or a pseudo-terminal: .IP TIOCGETP Get terminal parameters. .I arg is a pointer to a block of memory with the following structure: .nf 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 */ }; .fi .IP TIOCSETP Set terminal parameters from the struct sgttyb pointed to by .IR arg . .IP TIOCGETC Get terminal control characters. .I arg is a pointer to the following structure: .nf 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 */ }; .fi .IP TIOCSETC Set terminal control characters from the struct tchars pointed to by .IR arg . Setting any character to the value 0 causes the corresponding function to become unavailable. .IP TIOCGLTC Get extended terminal control characters, and put them in the structure pointed to by .IR arg : .nf 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 */ }; .fi .IP TIOCSLTC Set extended terminal control characters from the struct ltchars pointed to by .IR arg . Setting any of the characters to 0 causes the corresponding function to become unavailable. .IP TIOCGWINSZ .I arg has type "struct winsize *". The current window size for this window is placed in the structure pointed to by .IR arg , which has the following fields: .nf 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 */ }; .fi If any fields in the structure are 0, this means that the corresponding value is unknown. .IP TIOCSWINSZ .I arg has type "struct winsize *". The current window size for the window is set from the structure pointed to by .IR arg . Note that the kernel maintains the information but does .B 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. .IP TIOCGPGRP .I arg has type "long *"; the process group for the terminal is placed into the long pointed to by it. .IP TIOCSPGRP .I 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. .IP TIOCSTART Restart output to the terminal (as though the user typed control-Q) if it was stopped by a control-S or TIOCSTOP command. .I arg is ignored. .IP TIOCSTOP Stop output to the terminal (as though the user typed control-S). .I arg is ignored. .IP TIOCGXKEY Get the definition of a function or cursor key. .I arg is a pointer to a structure with the following fields: .nf struct xkey { short xk_num; /* function key number */ char xk_def[8]; /* associated string */ }; .fi The .I xk_num field must be initialized with the number of the desired key: .nf 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 .fi The string currently associated with the indicated key is copied into xk_def; this string is always null-terminated. .IP TIOCSXKEY .I arg is a structure of type struct xkey, as defined above. Both the .I xk_num and the .I xk_def fields must be defined. After execution of this command, and if the XKEY bit is set in the .I 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 .I Fread to read the key will get the string in .I xk_def instead of ASCII 0. Note that this translation occurs only for MiNT domain processes and only for the .I Fread system call. Also note that the string in .I xk_def must be null terminated, and so at most 7 characters may be assigned to any key. .PP The following commands are valid only for processes opened as files: .IP PBASEADDR .I arg is a pointer to a 32 bit integer, into which the address of the process basepage for the process to which .I fh refers is written. .IP PPROCADDR .I 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 .I PCTXTSIZE command. .IP PCTXTSIZE .I 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 .I PPROCADDR command. The first is the current process context; the second is the saved context from the last system call. .IP PGETFLAGS .I arg is a pointer to a 32 bit integer, into which the process memory allocation flags are copied. These flags are the same ones found in the `prgflags' field of GEMDOS executable programs, or as the first parameter to .I Pexec mode 7. .IP PSETFLAGS .I arg is a pointer to a 32 bit integer, from which the process memory flags for the target process will be set. Note that only the low order 16 bits are actually used right now, and not all of these are valid. See the documentation for GEMDOS executable programs for details on the meanings of the flags. .IP PTRACEGFLAGS .I arg is a pointer to a 16 bit integer, into which the current trace flags of the target process are copied. If the process is not being traced, the flags will be 0. .IP PTRACESFLAGS .I arg is a pointer to a 16 bit integer, the bits of which determine how the target process will respond to signals. If bit #0 is set, the target process will respond to signals and other exceptions by stopping, and the process which set the flags will receive a SIGCHLD signal informing it of this fact; it may then use the .I Pwait3 system call to retreive information about why the process stopped, and may use .I Fread and .I Fwrite to interrogate and possibly change the state of the process before causing it to continue (see below). If bit #0 is clear, then all process tracing will cease, and the process will respond to signals in the normal way. All other bits are reserved and should be set to 0 for now. If some other process has already used .I PTRACESFLAGS to set process tracing for the target process, then the call will fail. .IP PTRACEGO Restarts a process that was being traced by the caller and which stopped because of a signal. .I arg is a pointer to a 16 bit integer which is either 0 (in which case all pending signals for the stopped process are cleared before it is restarted) or the number of a signal which is to be delivered to the process after it restarts. Typically, this will be the same as the signal that stopped it. .IP PTRACESTEP Like .IR PTRACEGO , except that the trace bit will be set in the status register of the restarted process; thus, a SIGTRAP signal will be generated in that process after 1 user instruction has been executed. Note that it is not possible to trace processes that are executing in the kernel; if the process was stopped while executing in the kernel the trace bit will be set only when the process returns from the kernel. .IP PLOADINFO Returns information about the parameters passed to Pexec to start this process. .I arg should be a pointer to a structure with the following format: .nf struct ploadinfo { short fnamelen; /* length of fname field */ char *cmdlin; /* must point to 128 bytes, to be filled in with the process' command line */ char *fname; /* must point to "fnamelen" bytes, to be filled in with the full path+name of the file from which the process was launched */ } .fi The data pointed to by the structure elements will be filled in with the appropriate data for this process. If the process's full name and path are too long to fit into the provided space, ENAMETOOLONG will be returned. On success, a 0 is returned. .PP The following commands are valid only for files which represent shared memory. .IP SHMSETBLK .I arg is a pointer to a block of memory previously allocated by .IR Mxalloc . The memory will be offered for sharing under the name of the file represented by .I fd (which must be a file in the U:\\SHM subdirectory). .IP SHMGETBLK .I arg must be 0, for future compatibility. Returns the address of the block of memory previously associated with the file via .IR 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. .SH RETURNS 0 or a positive number if successful (for most commands; but see the specific descriptions above). .PP EIHNDL if .I fh is not a valid GEMDOS open handle. .PP EINVFN if the specified command is not valid for this file handle .PP Some other (LONG) negative error number if an error occurs; different commands may recognize different possible errors. .SH "SEE ALSO" .IR Fdup (2), .IR Flock (2), .IR Fopen (2), .IR Fxattr (2), .IR Pgetpgrp (2), .IR Psetpgrp (2) .SH BUGS Very little error checking is done. In particular, ownership of terminals is not properly checked, nor is read/write access to the files. Do not rely on this bug; it will be fixed some day. .PP File locking is not yet implemented for some file systems.