Does a shell automatically connect file descriptors 0, 1 and 2 to its controlling terminal?
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From The Linux Programming Interface
In an interactive shell, these three file
descriptors 0, 1 and 2 normally refer to the terminal under which the shell is running.
Does "the terminal under which the shell is running" mean the
controlling terminal of the session to which the interactive shell
belongs?If yes, what if the shell's session doesn't have a controlling terminal?
When the shell is created from its parent process, will the shell automatically create connection betwee file descriptors 0, 1 and 2 and the terminal, in each of
the following cases (inheritance from the parent process of the shell):if "the terminal under which the shell is running" or the controlling terminal has already been opened at a file descriptor
which is not 0, 1 and 2?if the file descriptors 0, 1 and 2 have already been connected to a file which is not "the terminal under which the shell is running"
or the controlling terminal?
- What if the shell in the quote is noninteractive?
Thanks.
Btw, just assume "shell" is POSIX or bash.
Related How can we disconnect a file descriptor from any file?
bash terminal io-redirection file-descriptors controlling-terminal
asked May 29 at 2:15
Tim
22.6k61222401
add a comment |Â
up vote
-3
down vote
favorite
From The Linux Programming Interface
In an interactive shell, these three file
descriptors 0, 1 and 2 normally refer to the terminal under which the shell is running.
Does "the terminal under which the shell is running" mean the
controlling terminal of the session to which the interactive shell
belongs?If yes, what if the shell's session doesn't have a controlling terminal?
When the shell is created from its parent process, will the shell automatically create connection betwee file descriptors 0, 1 and 2 and the terminal, in each of
the following cases (inheritance from the parent process of the shell):if "the terminal under which the shell is running" or the controlling terminal has already been opened at a file descriptor
which is not 0, 1 and 2?if the file descriptors 0, 1 and 2 have already been connected to a file which is not "the terminal under which the shell is running"
or the controlling terminal?
- What if the shell in the quote is noninteractive?
Thanks.
Btw, just assume "shell" is POSIX or bash.
Related How can we disconnect a file descriptor from any file?
bash terminal io-redirection file-descriptors controlling-terminal
asked May 29 at 2:15
Tim
22.6k61222401
1
The terminal opens FDs 0, 1, and 2 to whichever executable it runs. If the executable happens to be a shell then so be it.
– Ignacio Vazquez-Abrams
May 29 at 2:16
And if the terminal is connected over a port, like all real terminals used to be, (traditionally)initspawnsgettywhich opens the port and waits for a terminal to connect then execsloginwhich verifies the userid/password and usually (except for a restricted userid) execs a shell -- all with 0,1,2 on the terminal.
– dave_thompson_085
May 29 at 3:28
add a comment |Â
up vote
-3
down vote
favorite
up vote
-3
down vote
favorite
From The Linux Programming Interface
In an interactive shell, these three file
descriptors 0, 1 and 2 normally refer to the terminal under which the shell is running.
Does "the terminal under which the shell is running" mean the
controlling terminal of the session to which the interactive shell
belongs?If yes, what if the shell's session doesn't have a controlling terminal?
When the shell is created from its parent process, will the shell automatically create connection betwee file descriptors 0, 1 and 2 and the terminal, in each of
the following cases (inheritance from the parent process of the shell):if "the terminal under which the shell is running" or the controlling terminal has already been opened at a file descriptor
which is not 0, 1 and 2?if the file descriptors 0, 1 and 2 have already been connected to a file which is not "the terminal under which the shell is running"
or the controlling terminal?
- What if the shell in the quote is noninteractive?
Thanks.
Btw, just assume "shell" is POSIX or bash.
Related How can we disconnect a file descriptor from any file?
bash terminal io-redirection file-descriptors controlling-terminal
asked May 29 at 2:15
Tim
22.6k61222401
From The Linux Programming Interface
In an interactive shell, these three file
descriptors 0, 1 and 2 normally refer to the terminal under which the shell is running.
Does "the terminal under which the shell is running" mean the
controlling terminal of the session to which the interactive shell
belongs?If yes, what if the shell's session doesn't have a controlling terminal?
When the shell is created from its parent process, will the shell automatically create connection betwee file descriptors 0, 1 and 2 and the terminal, in each of
the following cases (inheritance from the parent process of the shell):if "the terminal under which the shell is running" or the controlling terminal has already been opened at a file descriptor
which is not 0, 1 and 2?if the file descriptors 0, 1 and 2 have already been connected to a file which is not "the terminal under which the shell is running"
or the controlling terminal?
- What if the shell in the quote is noninteractive?
Thanks.
Btw, just assume "shell" is POSIX or bash.
Related How can we disconnect a file descriptor from any file?
bash terminal io-redirection file-descriptors controlling-terminal
asked May 29 at 2:15
Tim
22.6k61222401
edited May 29 at 2:55
asked May 29 at 2:15
Tim
22.6k61222401
asked May 29 at 2:15
Tim
22.6k61222401
asked May 29 at 2:15
Tim
22.6k61222401
22.6k61222401
1
The terminal opens FDs 0, 1, and 2 to whichever executable it runs. If the executable happens to be a shell then so be it.
– Ignacio Vazquez-Abrams
May 29 at 2:16
And if the terminal is connected over a port, like all real terminals used to be, (traditionally)initspawnsgettywhich opens the port and waits for a terminal to connect then execsloginwhich verifies the userid/password and usually (except for a restricted userid) execs a shell -- all with 0,1,2 on the terminal.
– dave_thompson_085
May 29 at 3:28
add a comment |Â
1
The terminal opens FDs 0, 1, and 2 to whichever executable it runs. If the executable happens to be a shell then so be it.
– Ignacio Vazquez-Abrams
May 29 at 2:16
And if the terminal is connected over a port, like all real terminals used to be, (traditionally)initspawnsgettywhich opens the port and waits for a terminal to connect then execsloginwhich verifies the userid/password and usually (except for a restricted userid) execs a shell -- all with 0,1,2 on the terminal.
– dave_thompson_085
May 29 at 3:28
1
1
The terminal opens FDs 0, 1, and 2 to whichever executable it runs. If the executable happens to be a shell then so be it.
– Ignacio Vazquez-Abrams
May 29 at 2:16
The terminal opens FDs 0, 1, and 2 to whichever executable it runs. If the executable happens to be a shell then so be it.
– Ignacio Vazquez-Abrams
May 29 at 2:16
And if the terminal is connected over a port, like all real terminals used to be, (traditionally)
init spawns getty which opens the port and waits for a terminal to connect then execs login which verifies the userid/password and usually (except for a restricted userid) execs a shell -- all with 0,1,2 on the terminal.– dave_thompson_085
May 29 at 3:28
And if the terminal is connected over a port, like all real terminals used to be, (traditionally)
init spawns getty which opens the port and waits for a terminal to connect then execs login which verifies the userid/password and usually (except for a restricted userid) execs a shell -- all with 0,1,2 on the terminal.– dave_thompson_085
May 29 at 3:28
add a comment |Â
1 Answer
1
active
oldest
votes
up vote
3
down vote
accepted
No.
This is done by the various implementations of getty, by open-controlling-tty, by the forked pty-slave-side part of an SSH server, by the forked pty-slave-side part of a GUI terminal emulator, or some such.
And notice that the text quoted has no implication that the shell does this. You have created a whole load of questions based upon a false premise pulled out of thin air.
And you knew that getty does this, because you wrote that it did in "When is the process session led by login started?", written at the same time as this question.
Further reading
- What is the difference between getty and agetty?
- "askfirst" getty with systemd ("press enter to activate this console")
- Jonathan de Boyne Pollard. "Virtual terminal login". nosh Guide. Softwares.
- Jonathan de Boyne Pollard. "Real terminal login". nosh Guide. Softwares.
answered May 29 at 7:10
JdeBP
28k459133
Thanks. I think your nosh is great! I happened to have a problem which nosh's ulimit addresses, and still wonder about how to achieve the similar using regular commands: unix.stackexchange.com/questions/446539/…
– Tim
May 29 at 12:29
add a comment |Â
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
accepted
No.
This is done by the various implementations of getty, by open-controlling-tty, by the forked pty-slave-side part of an SSH server, by the forked pty-slave-side part of a GUI terminal emulator, or some such.
And notice that the text quoted has no implication that the shell does this. You have created a whole load of questions based upon a false premise pulled out of thin air.
And you knew that getty does this, because you wrote that it did in "When is the process session led by login started?", written at the same time as this question.
Further reading
- What is the difference between getty and agetty?
- "askfirst" getty with systemd ("press enter to activate this console")
- Jonathan de Boyne Pollard. "Virtual terminal login". nosh Guide. Softwares.
- Jonathan de Boyne Pollard. "Real terminal login". nosh Guide. Softwares.
answered May 29 at 7:10
JdeBP
28k459133
Thanks. I think your nosh is great! I happened to have a problem which nosh's ulimit addresses, and still wonder about how to achieve the similar using regular commands: unix.stackexchange.com/questions/446539/…
– Tim
May 29 at 12:29
add a comment |Â
up vote
3
down vote
accepted
No.
This is done by the various implementations of getty, by open-controlling-tty, by the forked pty-slave-side part of an SSH server, by the forked pty-slave-side part of a GUI terminal emulator, or some such.
And notice that the text quoted has no implication that the shell does this. You have created a whole load of questions based upon a false premise pulled out of thin air.
And you knew that getty does this, because you wrote that it did in "When is the process session led by login started?", written at the same time as this question.
Further reading
- What is the difference between getty and agetty?
- "askfirst" getty with systemd ("press enter to activate this console")
- Jonathan de Boyne Pollard. "Virtual terminal login". nosh Guide. Softwares.
- Jonathan de Boyne Pollard. "Real terminal login". nosh Guide. Softwares.
answered May 29 at 7:10
JdeBP
28k459133
Thanks. I think your nosh is great! I happened to have a problem which nosh's ulimit addresses, and still wonder about how to achieve the similar using regular commands: unix.stackexchange.com/questions/446539/…
– Tim
May 29 at 12:29
add a comment |Â
up vote
3
down vote
accepted
up vote
3
down vote
accepted
No.
This is done by the various implementations of getty, by open-controlling-tty, by the forked pty-slave-side part of an SSH server, by the forked pty-slave-side part of a GUI terminal emulator, or some such.
And notice that the text quoted has no implication that the shell does this. You have created a whole load of questions based upon a false premise pulled out of thin air.
And you knew that getty does this, because you wrote that it did in "When is the process session led by login started?", written at the same time as this question.
Further reading
- What is the difference between getty and agetty?
- "askfirst" getty with systemd ("press enter to activate this console")
- Jonathan de Boyne Pollard. "Virtual terminal login". nosh Guide. Softwares.
- Jonathan de Boyne Pollard. "Real terminal login". nosh Guide. Softwares.
answered May 29 at 7:10
JdeBP
28k459133
No.
This is done by the various implementations of getty, by open-controlling-tty, by the forked pty-slave-side part of an SSH server, by the forked pty-slave-side part of a GUI terminal emulator, or some such.
And notice that the text quoted has no implication that the shell does this. You have created a whole load of questions based upon a false premise pulled out of thin air.
And you knew that getty does this, because you wrote that it did in "When is the process session led by login started?", written at the same time as this question.
Further reading
- What is the difference between getty and agetty?
- "askfirst" getty with systemd ("press enter to activate this console")
- Jonathan de Boyne Pollard. "Virtual terminal login". nosh Guide. Softwares.
- Jonathan de Boyne Pollard. "Real terminal login". nosh Guide. Softwares.
answered May 29 at 7:10
JdeBP
28k459133
edited May 29 at 7:17
answered May 29 at 7:10
JdeBP
28k459133
answered May 29 at 7:10
JdeBP
28k459133
answered May 29 at 7:10
JdeBP
28k459133
28k459133
Thanks. I think your nosh is great! I happened to have a problem which nosh's ulimit addresses, and still wonder about how to achieve the similar using regular commands: unix.stackexchange.com/questions/446539/…
– Tim
May 29 at 12:29
add a comment |Â
Thanks. I think your nosh is great! I happened to have a problem which nosh's ulimit addresses, and still wonder about how to achieve the similar using regular commands: unix.stackexchange.com/questions/446539/…
– Tim
May 29 at 12:29
Thanks. I think your nosh is great! I happened to have a problem which nosh's ulimit addresses, and still wonder about how to achieve the similar using regular commands: unix.stackexchange.com/questions/446539/…
– Tim
May 29 at 12:29
Thanks. I think your nosh is great! I happened to have a problem which nosh's ulimit addresses, and still wonder about how to achieve the similar using regular commands: unix.stackexchange.com/questions/446539/…
– Tim
May 29 at 12:29
add a comment |Â
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1
The terminal opens FDs 0, 1, and 2 to whichever executable it runs. If the executable happens to be a shell then so be it.
– Ignacio Vazquez-Abrams
May 29 at 2:16
And if the terminal is connected over a port, like all real terminals used to be, (traditionally)
initspawnsgettywhich opens the port and waits for a terminal to connect then execsloginwhich verifies the userid/password and usually (except for a restricted userid) execs a shell -- all with 0,1,2 on the terminal.– dave_thompson_085
May 29 at 3:28