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Top Forums Programming Fork and Execvp Not Executing Bash Commands From C correctly. Post 302969174 by bakunin on Saturday 19th of March 2016 04:16:24 AM
Old 03-19-2016
To expand on what Don Cragun already said:

A commandline like

Code:
command1 | command2

is not "a process" but in fact the shell creates two such processes: one for "command1", one for "command2". You need to execute the procedure of using execvp() or fork() for both of them because both are processes in their own right. Only then you need a provision for the pipeline functionality.

A (shell-) pipeline is to connect STDOUT of the one process to the STDIN of the other. But this means there are already two process-environments with such file descriptors that can be connected. Here is a thread that might give you the picture: Trouble with pipes in chat client on linux.

I hope that helps.

bakunin
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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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