You can always check the man page of your shell. man bash says: Special Parameters # Expands to the number of positional parameters in decimal. Therefore a shell script can check …

In shell terminology, eval is a built-in, not a function. In practice, built-ins behave a lot like functions that don't have an in-language definition, but not quite (as becomes apparent if you …

Kernel Version. If you want kernel version information, use uname(1). For example: $ uname -a Linux localhost 3.11.0-3-generic #8-Ubuntu SMP Fri Aug 23 16:49:15 UTC 2013 x86_64 …

Aug 17, 2012 · If rm -r doesn't work, that would be an OS issue, not a shell issue. (Strictly speaking, it would be an issue with the version of rm that you're using, so you could address it …

You can find a very nice reference for bash's [aka test builtin's operators here, or by running help test in a bash shell or info bash test or info bash '[' from any shell¹. If you are using a different …

On many systems booting into single user mode will give the user access to a root shell without prompting for a password. Notably, systemd-based systems will prompt you for the root …

It's probably the most common command to use in an if, which can lead to the assumption that it's part of the shell's syntax. But if you want to test whether a command succeeded or not, use …

In man bash we can read in Shell Builtin Commands section : Unless otherwise noted, each builtin command documented in this section as accepting options preceded by -accepts --to …

Oct 23, 2013 · The only thing that you need to be aware of when using this method is that all modifications of Shell variables done from the command you pass to run will not propagate to …

Oct 27, 2010 · Generally, you can use sudo to launch a new shell as the user you want; the -u flag lets you specify the username you want: $ whoami user1 $ sudo -u user2 zsh $ whoami …