The ioctl system call.

[cascardo/kernel/old_slides/.git] / _ldd.xml

diff --git a/_ldd.xml b/_ldd.xml
index 2b20507..fbc7570 100644 (file)
--- a/_ldd.xml
+++ b/_ldd.xml
@@ -56,7 +56,7 @@ write
 close
 </para></listitem>
 <listitem><para>
-seek
+lseek
 </para></listitem>
 <listitem><para>
 ioctl
@@ -86,4 +86,108 @@ fd = open ("/dev/ttyS0", O\_RDWR);
 </para>
 </foil>
 
+<foil>
+<title>close</title>
+<para>
+The close system call closes an open file.
+</para>
+<para>
+int close (int fd);
+</para>
+<para>
+Example:
+</para>
+<para>
+close (fd);
+</para>
+</foil>
+
+<foil>
+<title>read</title>
+<para>
+The read system call reads data from an open file into a buffer. For
+devices, it reads from the device.
+</para>
+<para>
+int read (int fd, char *buffer, int bsz);
+</para>
+<para>
+Read returns the number of bytes written into the buffer, which may be
+less than the number of bytes requested for any number of reasons.
+</para>
+<para>
+Example:
+</para>
+<para>
+c = read (fd, buffer, sizeof (buffer));
+</para>
+</foil>
+
+<foil>
+<title>write</title>
+<para>
+The write system call writes data to an open file from a buffer. For
+devices, it writes to the device.
+</para>
+<para>
+int write (int fd, char *buffer, int bsz);
+</para>
+<para>
+Write returns the number of bytes written to the file, which may be
+less than the number of bytes requested for any number of reasons.
+</para>
+<para>
+Example:
+</para>
+<para>
+c = write (fd, buffer, strlen (buffer));
+</para>
+</foil>
+
+<foil>
+<title>lseek</title>
+<para>
+The lseek system call changes the current position of the file, allowing
+to read or write in that position. Seeking on a device may have many
+different meanings.
+</para>
+<para>
+off\_t lseek (int fd, off\_t pos, int whence);
+</para>
+<para>
+The meaning of the position depends on the value of whence, which can be
+SEEK\_SET (the absolute position), SEEK\_CUR (relative to the current
+position), SEEK\_END (relative to the end of the file).
+</para>
+<para>
+Example:
+</para>
+<para>
+lseek (fd, 0, SEEK\_END);
+</para>
+</foil>
+
+<foil>
+<title>ioctl</title>
+<para>
+The ioctl system call is a catch-all operation. For those operations
+which doesn't fit in the read/write model, the ioctl allows the user to
+send a command with an optional argument to the device. This command may
+accept input or generate output.
+</para>
+<para>
+int ioctl (int fd, int request, char *arg);
+</para>
+<para>
+The last argument is optional and depends on the type of request. Every
+device or device class may have its different set of ioctl's.
+</para>
+<para>
+Example:
+</para>
+<para>
+struct ifreq req; ioctl (fd, SIOCGIFFLAGS, \&#38;req);
+</para>
+</foil>
+
 </slides>