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ShellBuiltinNotes version 5, including all changes.
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IanMcDonald |
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In Unix, a shell builtin is a command or a function, called from a [Shell], that is executed directly in the shell itself, instead of an external executable program which the shell would load and execute. |
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BenStaz |
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!How can I tell if the command I am using is a shell builtin rather than an external program? |
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*type <command_name> |
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<verbatim> |
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BenStaz |
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$ type cd |
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BenStaz |
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cd is a shell builtin |
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BenStaz |
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$ type mkdir |
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BenStaz |
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mkdir is /bin/mkdir |
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</verbatim> |
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BenStaz |
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!But I want to use an external program rather than a shell-builtin. |
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If a command specified to the shell contains a slash ''/'', the shell will not execute a builtin command. Thus, while specifying ''echo'' causes a builtin command to be executed under shells that support the builtin echo command, specifying ''/bin/echo'' does not. |
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!Why can I not use ''sudo <shell_builtin>'' ? |
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BenStaz |
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A shell builtin is not an executable file so sudo does not know about it. (obviously wont be found in any dirs in sudo's PATH). |
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BenStaz |
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You will need to use the command ''sudo -s'' to get a new shell with root privileges or alternatively you can do ''sudo bash -c "<shell_builtin>" ~[args~]''. |
