isatty is a function for checking this, and the -t flag of the test command makes that accessible from a shell script:

-t file_descriptor

True if file descriptor number file_descriptor is open and is associated with a terminal. False if file_descriptor is not a valid file descriptor number, or if file descriptor number file_descriptor is not open, or if it is open but is not associated with a terminal.

You can check if FD 0 (standard input) is a TTY with:

test -t 0

You can do the same for FDs 1 and 2 to check the output and error streams, or all of them:

test -t 0 -a -t 1 -a -t 2

The command returns 0 (succeeds) if the descriptors are hooked up to a terminal, and is false otherwise.

test is also available as a "bracket test":

 if [ -t 0 ] ; then ...

is an idiomatic way to write this conditional.

isatty is a function for checking this, and the -t flag of the test command makes that accessible from a shell script:

-t file_descriptor

True if file descriptor number file_descriptor is open and is associated with a terminal. False if file_descriptor is not a valid file descriptor number, or if file descriptor number file_descriptor is not open, or if it is open but is not associated with a terminal.

You can check if FD 0 (standard input) is a TTY with:

test -t 0

You can do the same for FDs 1 and 2 to check the output and error streams, or all of them:

test -t 0 -a -t 1 -a -t 2

The command returns 0 (succeeds) if the descriptors are hooked up to a terminal, and is false otherwise.

test is also available as the [ command for a "bracket test":

 if [ -t 0 ] ; then ...

is an idiomatic way to write this conditional.

isatty is a function for checking this, and the -t flag of the test command makes that accessible from a shell script:

-t file_descriptor

True if file descriptor number file_descriptor is open and is associated with a terminal. False if file_descriptor is not a valid file descriptor number, or if file descriptor number file_descriptor is not open, or if it is open but is not associated with a terminal.

You can check if FD 0 (standard input) is a TTY with:

test -t 0

You can do the same for FDs 1 and 2 to check the output and error streams, or all of them:

test -t 0 -a -t 1 -a -t 2

The command returns 0 (succeeds) if the descriptors are hooked up to a terminal, and is false otherwise.

test is also available as [: if [ -t 0 ] ; then ... is an idiomatic way to write this conditional.

isatty is a function for checking this, and the -t flag of the test command makes that accessible from a shell script:

-t file_descriptor

True if file descriptor number file_descriptor is open and is associated with a terminal. False if file_descriptor is not a valid file descriptor number, or if file descriptor number file_descriptor is not open, or if it is open but is not associated with a terminal.

You can check if FD 0 (standard input) is a TTY with:

test -t 0

You can do the same for FDs 1 and 2 to check the output and error streams, or all of them:

test -t 0 -a -t 1 -a -t 2

The command returns 0 (succeeds) if the descriptors are hooked up to a terminal, and is false otherwise.

test is also available as a "bracket test":

 if [ -t 0 ] ; then ...

is an idiomatic way to write this conditional.