file system3.txt

Linux C 语言函数

fsync

SYNOPSIS
int fsync(int fd); 


DESCRIPTION
Synchronizes the state of the file on disk with the state of the file in core. (For one 
thing, it flushes the file buffers.) 


PARAMETERS
fd: [in] the file to sync. 


RETURN VALUE
On success zero is returned. On error, -1 is returned and errno is set to one of: EINVAL, 
EBADF or EIO. 


****************************************************************************************
ftruncate and truncate

SYNOPSIS
int ftruncate(int fd, size_t length); 

int truncate(char *path, size_t length); 


DESCRIPTION
Those calls truncate a file to a specified length. In the case of ftruncate, the file must 
be opened for writing. 


PARAMETERS
fd: [in] the file descriptor to truncate. 

path: [in] points to the path of the file to truncate. 

length: [in] the new size of the file. 


RETURN VALUE
On success zero is returned. On error, -1 is returned and errno is set to one of the 
following values: 

for ftruncate: 

ENOENT: the file is invalid. 
EBADF, EACCESS. 

for truncate: 

ENOTDIR, EINVAL, ENAMETOOLONG, ENOENT, EACCESS, ELOOP, EISDIR, EROFS, ETXTBSY, EIO or 
EFAULT.


****************************************************************************************
ioctl

SYNOPSIS
int ioctl(int d, int cmd, ...); 

The third argument is called char *argp. 


PARAMETERS
d: [in] the file descriptor of the file to manipulate. 

cmd: [in] the type of request. 

argp: depends on the request. 


DESCRIPTION
Controls the io parameters of character special devices (tty, mt, etc.). The values that 
cmd may take for file operations are: 


FIOCLEX 
Sets the close-on-exec flag of the file. 

FIONCLEX 
Clears the close-on-exec flag of the file. 

FIONBIO 
If argp is true, sets the file O_NONBLOCK flag, otherwise it clears the flag. 

FIOASYNC 
If argp is true, sets the file O_SYNC flag, otherwise it clears the flag. (This flag is not
used as of Linux 1.0.) 

FIONREAD 
Returns to a buffer pointed to by argp, the number of bytes immediately readable from the 
file. 

FIOSETOWN 
Sets the owner of the file to argp (a pid). The owner is the one that receives the SIGURG 
and SIGIO signals. (Only for sockets.) 

FIOGETOWN 
Returns the owner of the file to a buffer pointed to by argp. (Only for sockets.) 

FIGETBSZ 
Returns the block size of the file to a buffer pointed to by argp. (Seems non-standard.) 

FIBMAP 
Returns the block number in the fs corresponding to the argp'th block in the file. (I have 
guessed right? Anyway, this is non-standard.) 

The values for magnetic tape operations are: 

MTIOCTOP 
Perform an operation on a magnetic tape. argp is a pointer to a mtop structure. 

MTIOCGET 
Get magnetic tape status. argp is a pointer to a mtget structure. 

MTIOCPOS 
Set magnetic tape position. argp points to a long integer specifying the block number to go
to. 
The section on magnetic tapes will remain incomplete for a while... I don't have a clue how
it is supposed to work. 

The values for sockets operations are: 


SIOCSPGRP 
Same as FIOSETOWN. 

SIOCGPGRP 
Same as FIOGETOWN. 

SIOCATMARK 
Not supported. 

SIOCADDRT 
Adds a routing entry in the routing table of the system. The task must have superuser 
privileges to perform that operation. argp points to a rtentry structure. 

SIOCDELRT 
Removes a routing entry from the routing table of the system. The task must have superuser 
privileges to perform that operation. argp points to a rtentry structure. 

SIOCADDRTOLD 
Same as SIOCADDRT but uses an old_rtentry structure. Obsolete. Do not use. 

SIOCDELRTOLD 
Same as SIOCDELRT but uses an old_rtentry structure. Obsolete. Do not use. 

SIOCDARP 
Deletes an ARP entry. The calling task must have superuser privileges. argp points to an 
arpreq structure. 

SIOCGARP 
Retreive an ARP entry. The calling task must have superuser privileges. argp points to an 
arpreq structure. 

SIOCSARP 
Sets an ARP entry. The calling task must have superuser privileges. argp points to an 
arpreq structure. 

IP_SET_DEV 
Not supported. 

SIOCGIFCONF 
Reteives the network interface configuration list in a ifconf structure. 

SIOCGIFFLAGS 
Gets the interface flags. argp points to an ifreq structure. 

SIOCSIFFLAGS 
Sets the interface flags. argp points to an ifreq structure. The calling task must have 
superuser privileges. 

SIOCGIFADDR 
Gets the interface address. argp points to an ifreq structure. 

SIOCSIFADDR 
Sets the interface address. argp points to an ifreq structure. The calling task must have 
superuser privileges. 

SIOCGIFDSTADDR 
Gets the interface remote address. argp points to an ifreq structure. 

SIOCSIFDSTADDR 
Sets the interface remote address. argp points to an ifreq structure. The calling task must
have superuser privileges. 

SIOCGIFBRDADDR 
Gets the interface broadcast address. argp points to an ifreq structure. 

SIOCSIFBRDADDR 
Sets the interface broadcast address. argp points to an ifreq structure. The calling task 
must have superuser privileges. 

SIOCGIFNETMASK 
Gets the interface network mask. argp points to an ifreq structure. 

SIOCSIFNETMASK 
Sets the interface network mask. argp points to an ifreq structure. The calling task must 
have superuser privileges. 

SIOCGIFMETRIC 
Gets the interface routing metric. argp points to an ifreq structure. 

SIOCSIFMETRIC 
Sets the interface routing metric. argp points to an ifreq structure. The calling task must
have superuser privileges. 

SIOCGIFMEM or SIOCSIFMEM 
Not supported. 

SIOCGIFMTU 
Gets the interface maximum transmission unit. argp points to an ifreq structure. 

SIOCSIFMTU 
Sets the interface maximum transmission unit. argp points to an ifreq structure. The calling
task must have superuser privileges. 

SIOCSIFLINK 
Links in an I/O driver into the operating system kernel. 

SIOCGIFHWADDR 
Gets the interface hardware address. argp points to an ifreq structure. 

SIOCSIFHWADDR 
Not supported. 

SIOCGIFNAME 
Not supported. 

DDIOCSDBG: 
Set the DDI debug level. 

struct rtentry {
        unsigned long   rt_hash;        /* hash key for lookups         */
        struct sockaddr rt_dst;         /* target address               */
        struct sockaddr rt_gateway;     /* gateway addr (RTF_GATEWAY)   */
        struct sockaddr rt_genmask;     /* target network mask (IP)     */
        short           rt_flags;
        short           rt_refcnt;
        unsigned long   rt_use;
        struct ifnet    *rt_ifp;
        short           rt_metric;      /* +1 for binary compatibility! */
        char            *rt_dev;        /* forcing the device at add    */
};


struct old_rtentry {
        unsigned long   rt_genmask;
        struct sockaddr rt_dst;
        struct sockaddr rt_gateway;
        short           rt_flags;
        short           rt_refcnt;
        unsigned long   rt_use;
        char            *rt_dev; 
};

rt_flags is a or'ed combinaison of one or more of the following: 


RTF_UP 
the route is usable. 

RTF_GATEWAY 
the destination is a gateway. 

RTF_HOST 
the entry is a host. (If this flag is not set, the entry is a net.) 

struct arpreq {
  struct sockaddr       arp_pa;         /* protocol address             */
  struct sockaddr       arp_ha;         /* hardware address             */
  int                   arp_flags;      /* flags                        */
};

The arp_flags member may be one or more or'ed values of the following: 


ATF_INUSE 
the entry is in use. 

ATF_COM 
the entry is complete (ha is valid). 

ATF_PERM 
the entry is permanent. 

ATF_PUBL 
publish entry. 

ATF_USETRAILERS 
has requested trailers. 
Here is the layout of the ifconf structure used to get the configuration list: 


struct ifconf {
        int     ifc_len;                        /* size of buffer       */
        union {
                caddr_t ifcu_buf;
                struct  ifreq *ifcu_req;
        } ifc_ifcu;
};

Here is the layout of the ifreq structure used to send/receive interface data: 


struct ifreq {
#define IFHWADDRLEN     6
#define IFNAMSIZ        16
    union {
        char    ifrn_name[IFNAMSIZ];            /* if name, e.g. "en0" */
        char    ifrn_hwaddr[IFHWADDRLEN];
    } ifr_ifrn;
    union {
        struct  sockaddr ifru_addr;
        struct  sockaddr ifru_dstaddr;
        struct  sockaddr ifru_broadaddr;
        struct  sockaddr ifru_netmask;
        short   ifru_flags;
        int     ifru_metric;
        int     ifru_mtu;
        caddr_t ifru_data;
    } ifr_ifru;
};

For terminal I/O, the following commands may be used: 


TCGETS 
Gets the termios structure associated with the terminal. argp points to a termios structure. 

TCSETS 
Sets the termios structure associated with the terminal. The change is immediate. argp 
points to a termios structure. 

TCSETSW 
Same as TCSETS but wait until the output buffer is empty before performing the change. 

TCSETSF 
Same as TCSETS but wait until the output buffer is empty and flushes the input buffer before
performing the change. 

TCGETA 
Gets the termio structure associated with the terminal. argp points to a termio structure. 

TCSETS 
Sets the termio structure associated with the terminal. The change is immediate. argp points
to a termio structure. 

TCSETAW 
Same as TCSETA but wait until the output buffer is empty before performing the change. 

TCSETAF 
Same as TCSETA but wait until the output buffer is empty and flushes the input buffer before
performing the change. 

TCXONC 
Starts or stops the tty flow. argp may be one of the following: 

TCOOFF 
Stops output. 

TCOON 
Restart output. 

TCIOFF 
Stops input. 

TCION 
Restart input. 

TCFLSH 
Flushes the tty. argp may be TCIFLUSH to flush the input, TCOFLUSH to flush the output or 
TCIOFLUSH to flush both. 

TIOCEXCL 
Sets the tty in exclusive mode. No further open operations on the terminal are permited. 

TIOCNXCL 
Disable exclusive mode. open operations are now permitted. 

TIOCSCTTY 
Sets that termial as the controlling terminal of the current task. The calling task must be
a session leader and not have a controlling tty already. If the task does not have superuser 
privileges, normal authorisations checks are performed. If the task has superuser privileges 
and argp is set to 1, the terminal will be set as the controling terminal even if it was 
already the controling terminal of another task. 

TIOCGPGRP 
Gets the process group id associated with this terminal. argp points to an integer that is 
set to that id. 

TIOCSPGRP 
Associate the terminal to the process group which has an id equals to argp. The processes of
the process group must have the same real or saved uid of as the effective or save uid of 
the calling task, or be descendants of the calling process or the calling process must have
superuser privileges. 

TIOCOUTQ 
Sets an integer pointed to by argp to the number of bytes in the output queue that are not 
sent. 

TIOCSTI 
Insert the value of argp into the input queue of the terminal. 

TIOCGWINSZ 
Returns the window size into a winsize structure pointed to by argp. 

TIOCSWINSZ 
Sets the window size to the winsize structure pointed to by argp. 

TIOCCONS 
Controls the redirection of the console. If fd is a console, the redirection is cancelled. 
If fd is a pseudo console slave, the console is redirected to that slave. If fd is a 
pseudo console master, the console is redirected to its slave. The calling taks must be have
superuser privileges. 

TIOCNOTTY 
Dissociate the controling terminal from the current task. The calling task must be process 
leader. 

TIOCGETD 
Retreives the terminal current line discipline mode. The value is store to the area pointed
to by argp. 

TIOCSETD 
Sets the terminal line discipline mode to the value of argp. 

TIOCGLCKTRMIOS 
Gets the locking status of the termios structure of the terminal. argp points to a termios 
structure. 

TIOCSLCKTRMIOS 
Sets the locking status of the termios structure of the terminal. argp points to a termios 
structure that contains the new flags. The calling task must have superuser privileges. 

TIOCPKT 
If argp is 1, it sets the packet flag in the tty structure, otherwise it sets the flag to 
zero. (What purpose does that serves?) 

TIOCLINUX 
Linux dependent. 

TCSBRK 
Waits for the output queue to become empty, then, if argp is 1, sends a break. 

TCSBRKP 
Same as TCSBRK? 

RETURN VALUE
On success zero is returned. On error, -1 is returned and errno is set to one of the 
following values: 


EINVAL: cmd or argp have an invalid value. 
ENOTTY: d is not a character special device or the request made on d is not valid for this 
type of device. 
EBADF.