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Top Forums Shell Programming and Scripting Bash script unable to disable expected output Post 303016763 by SkySmart on Thursday 3rd of May 2018 10:17:31 AM
Old 05-03-2018
Bash script unable to disable expected output

I'm trying to understand why a script behaves different when run through a pipe.

My OS:

Code:
Linux  myip 3.13.0-92-generic #139-Ubuntu SMP Tue Jun 28 20:42:26 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

This script (myscript.sh):

Code:
#!/bin/bash

echo whoami:
whoami
echo who:
who
echo who am i:
who am i
echo logname:
logname

Gives the expected output of:

Code:
whoami
ubuntu
who
ubuntu   pts/1        2018-05-03 14:15 (8.21.68.241)
who am i
ubuntu   pts/1        2018-05-03 14:15 (8.21.68.241)
logname
ubuntu

But when run like through a pipe, the "who am i" command does not show the same output. doesnt show anything at all.

Code:
ubuntu@myIp:~$ cat ~/myscript.sh | bash
whoami:
ubuntu
who:
ubuntu   pts/1        2018-05-03 14:15 (8.21.68.241)
who am i:
logname:
ubuntu


What could be the problem? How can i get the piped way of running the script behave exactly as how the script would behave if run the regular way?
 

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RBASH(1)						      General Commands Manual							  RBASH(1)

NAME
rbash - restricted bash, see bash(1) RESTRICTED SHELL
If bash is started with the name rbash, or the -r option is supplied at invocation, the shell becomes restricted. A restricted shell is used to set up an environment more controlled than the standard shell. It behaves identically to bash with the exception that the follow- ing are disallowed or not performed: o changing directories with cd o setting or unsetting the values of SHELL, PATH, ENV, or BASH_ENV o specifying command names containing / o specifying a file name containing a / as an argument to the . builtin command o specifying a filename containing a slash as an argument to the -p option to the hash builtin command o importing function definitions from the shell environment at startup o parsing the value of SHELLOPTS from the shell environment at startup o redirecting output using the >, >|, <>, >&, &>, and >> redirection operators o using the exec builtin command to replace the shell with another command o adding or deleting builtin commands with the -f and -d options to the enable builtin command o using the enable builtin command to enable disabled shell builtins o specifying the -p option to the command builtin command o turning off restricted mode with set +r or set +o restricted. These restrictions are enforced after any startup files are read. When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script. SEE ALSO
bash(1) GNU Bash-4.0 2004 Apr 20 RBASH(1)
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