About

TODO introduction + "Philosophy and Architecture"

jsh: A basic UNIX shell implementation in C. jsh is free software and makes use of the GNU Readline library for input line editing and history.

Configuration files:

• ~/.jshrc: file containing commands to be executed at login
• ~/.jsh_history: containing the command history auto loaded and saved at login/logout
• ~/.jsh_login: file containing the ASCII welcome message auto printed at login of an interactive session

Supported options:

• -h, --help display the help message
• -d, --debug turn printing of debug messages on
• -n, --nodebug turn printing of debug messages on
• -c, --color turn coloring of jsh output messages on
• -o, --nocolor turn coloring of jsh output messages off
• -f, --norc disable autoloading of the ~/.jshrc file
• -l, --license display licence information

Supported shell grammar

The following recursive grammar is currently supported.

 input  :=    expr

 expr   :=    <space>expr         // expr is a logical combination of cmds
              expr<space>
              expr #comment
              "expr"
              (expr)
              expr ; expr
              expr && expr
              expr || expr
              cmd

 cmd    :=    cmd | cmd           // cmd is the unit of truth value evaluation
              cmd >> path         // note: pipe redirection get priority over explicit redirection
              cmd 2> path
              cmd > path
              cmd < path
              cmd &               *TODO not yet implemented
              comd

 comd   :=    comd option         // comd is the unit of fork / built_in
              alias               // note priority: alias > built_in > executable
              built_in
              executable_path     // relative (using the PATH env var) or absolute

 alias  :=    (expr)              // alias is a symbolic linkt to an expr

Built in shell commands

The jsh shell can execute any executable, identified by either an absolute or relative path (using the PATH environment variable). Alongside it also supports some built_in shell commands. This is a list of currently supported built_ins:

• cd
• color
• debug
• exit
• history
• shcat
• source
• alias // syntax: alias key "value with spaces"
• unalias