Of Zeros and Nulls

              /dev/zero ... /dev/null

Uses of /dev/null

Think of /dev/null as a black hole. It is essentially the equivalent of a write-only file. Everything written to it disappears. Attempts to read or output from it result in nothing. All the same, /dev/null can be quite useful from both the command line and in scripts.

/dev and /proc in Linux

Table of Contents

A Linux or UNIX machine typically has the /dev and /proc special-purpose directories.

Arrays in Shell Scripting

                   Newer versions of Bash support one-dimensional arrays. Array elements may be initialized with the variable[xx] notation. Alternatively, a script may introduce the entire array by an explicit declare -a variable statement. To dereference (retrieve the contents of) an array element, use curly bracket notation, that is, ${element[xx]}.

List Constructs

                     The and list and or list constructs provide a means of processing a number of commands consecutively. These can effectively replace complex nested if/then or even case statements.

Aliases in Shell Script

              A Bash alias is essentially nothing more than a keyboard shortcut, an abbreviation, a means of avoiding typing a long command sequence. If, for example, we include alias lm="ls -l | more" in the ~/.bashrc file, then each lm typed at the command line will automatically be replaced by a ls -l | more. This can save a great deal of typing at the command line and avoid having to remember complex combinations of commands and options. Setting alias rm="rm -i" (interactive mode delete) may save a good deal of grief, since it can prevent inadvertently losing important files.