Command language

qsh is a program that:

• reads input from either a file or a terminal
• breaks the input into tokens
• parses the input into simple and compound commands
• performs various expansions on each command
• performs redirection of input and output
• runs the commands
• optionally waits for the commands to complete

qsh implements a command language that has flow control constructs, variables, and functions. The interpretative language is common to both interactive and non-interactive use (shell scripts). So the same commands that are entered at an interactive command line can also be put in a file and the file can be run directly by qsh.

For more information about particular features of qsh, see the following topics:

Quoting
Select this link to view information about quoting, including the escape character, literal quotes, and grouping quotes.

Parameters
Select this link to view information about parameters, including positional parameters and special parameters.

Variables
Select this link to view information about variables, including the variables set by and variables used by qsh.

Word expansions
Select this link to view information about word expansions, including tilde expansion, parameter expansion, command substitution, arithmetic expansion, field splitting, path name expansion, and quote removal.

Redirection
Select this link to view information about input and output redirections.

Simple commands
Select this link to view information about running simple commands.

Pipelines
Select this link to view information about running multiple commands in a pipeline.

Lists
Select this link to view information about running multiple commands in a list.

Compound commands
Select this link to view information about compound commands, including grouping commands, conditional commands, loop commands, and functions.