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Bash, zsh and fish offer parameter name completion through a definition external to the command, distributed in a separate completion definition file. For command parameter name/value completions, these shells assume path/filename completion if no completion is defined for the command.
Unix abstracts the nature of this tree hierarchy entirely and in Unix and Unix-like systems the root directory is denoted by the / (slash) sign. Though the root directory is conventionally referred to as /, the directory entry itself has no name – its path is the "empty" part before the initial directory separator character (/).
In a Unix shell, the full stop called the dot command (.) is a command that evaluates commands in a computer file in the current execution context. [1] In the C shell, a similar functionality is provided as the source command, [2] and this name is seen in "extended" POSIX shells as well.
The C shell also introduced many features for interactive work, including the history and editing mechanisms, aliases, directory stacks, tilde notation, cdpath, job control and path hashing. On many systems, csh may be a symbolic link or hard link to TENEX C shell (tcsh), an improved version of Joy's original version.
The most common form of aliases, which just add a few options to a command and then include the rest of the command line, can be converted easily to shell functions following this pattern: alias ll = 'ls -Flas' # long listing, alias ll () { ls -Flas " $@ " ; } # long listing, function
The example ~/.bash_profile below is compatible with the Bourne shell and gives semantics similar to csh for the ~/.bashrc and ~/.bash_login. The [ -r filename] && cmd is a short-circuit evaluation that tests if filename exists and is readable, skipping the part after the && if it is not.
The more command was originally written by Daniel Halbert, a graduate student at the University of California, Berkeley, in 1978.It was later expanded on by Eric Shienbrood, Geoff Peck (added underlining, single spacing) and John Foderaro (added -c, more environment variable history).
If pushd is not provided with a path argument, in Unix it instead swaps the top two directories on the stack, which can be used to toggle between two directories. The popd command removes (or 'pops', in the stack analogy) the current path entry from the stack and returns to the path at the top of the stack as the new working directory. [4] [5]