What Is Special About /Dev/Tty? [Closed]
Ls -La /Dev/Tty Shows the Output: Crw-Rw-Rw- 1 Root Tty 5, 0 Dec 14 22:21 /Dev/Tty What Does C at the Beginning Mean? When I Do Something Like Pwd > /Dev/Tty...
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ls -la /dev/tty shows the output:
crw-rw-rw- 1 root tty 5, 0 Dec 14 22:21 /dev/tty
What does c at the beginning mean? When I do something like pwd > /dev/tty it prints to the stdout. What does the file /dev/tty contain?
The 'c' means it's a character device. tty is a special file representing the 'controlling terminal' for the current process.
Character Devices
Unix supports 'device files', which aren't really files at all, but file-like access points to hardware devices. A 'character' device is one which is interfaced byte-by-byte (as opposed to buffered IO).
TTY
/dev/tty is a special file, representing the terminal for the current process. So, when you echo 1 > /dev/tty, your message ('1') will appear on your screen. Likewise, when you cat /dev/tty, your subsequent input gets duplicated (until you press Ctrl-C).
/dev/tty doesn't 'contain' anything as such, but you can read from it and write to it (for what it's worth). I can't think of a good use for it, but there are similar files which are very useful for simple IO operations (e.g. /dev/ttyS0 is normally your serial port)
This quote is from :
/dev/tty stands for the controlling terminal (if any) for the current process. To find out which tty's are attached to which processes use the "ps -a" command at the shell prompt (command line). Look at the "tty" column. For the shell process you're in, /dev/tty is the terminal you are now using. Type "tty" at the shell prompt to see what it is (see manual pg. tty(1)). /dev/tty is something like a link to the actually terminal device name with some additional features for C-programmers: see the manual page tty(4).
Here is the man page:
/dev/tty is a synonym for the controlling terminal (if any) of the current process. As jtl999 says, it's a character special file; that's what the c in the ls -l output means.
man 4 tty or man -s 4 tty should give you more information, or you can read the man page online here.
Incidentally, pwd > /dev/tty doesn't necessarily print to the shell's stdout (though it is the pwd command's standard output). If the shell's standard output has been redirected to something other than the terminal, /dev/tty still refers to the terminal.
You can also read from /dev/tty, which will normally read from the keyboard.
The 'c' means it's a character special file.
Sarah Jenkins is a veteran tech journalist with over 12 years of experience covering artificial intelligence, mobile innovations, and digital ethics. Her insights have appeared in leading technology publications worldwide.
