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 …

The echo shows the new directory not the previous one. And I would find it useful, so that I know where I am now, especially if I'm in a shell that only shows the current directory name (or …

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 …

Jun 14, 2013 · Using POSIX shell functions, and awk math power, just define this (one line) function: calc(){ awk "BEGIN { print $*}"; } Then just execute things like calc 1+1 or calc 5/2. …