5
votes
2answers
98 views

Default preference of executable over built-ins with the same name

I was playing around a bit with the names of some executables, putting them in a folder, ~/bin, which is in my $PATH. Now I'm wondering how I can set the preferences of a bash-3.2 terminal so that it ...
1
vote
1answer
330 views

A command that gives username@hostname:pwd

I know that pwd gives the current working directory, hostname gives the current host and whoami gives the current user. Is there a single unix command that will give me the output of ...
1
vote
3answers
554 views

how does built in commands of a shell implemented in Linux? as a function or thread of shell process?

I know that external commands are run in the shell by creating a separate process. But what exactly happens when a built in command is run in a shell. Are they executed as a function or if the shell ...
3
votes
1answer
136 views

the return built-in

According to the Open Group, [t]he return utility shall cause the shell to stop executing the current function or dot script. If the shell is not currently executing a function or dot script, ...
9
votes
2answers
254 views

What is not shell specific?

Under some answers, I see comments that recommend avoiding shell specific commands in answers. How do I know which commands, operators, etc exist in all shells? Is there a list of standards? man ...
32
votes
4answers
3k views

What is the difference between a builtin command and one that is not?

Is there any intrinsic difference between a builtin command and another command which can nominally do the same thing? eg. Do builtins get "special" treatement? ... is there less overhead running ...
19
votes
5answers
3k views

Why is echo a shell built in command?

$ which echo echo: shell built-in command. $ which ls /bin/ls $ which cat /bin/cat Why is echo not an independent utility like ls, ps, cat etc? Why is it shell specific? Any good reasons?