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eshell: Built-ins

 
 2.3 Built-in commands
 =====================
 
 Several commands are built-in in Eshell.  In order to call the external
 variant of a built-in command ‘foo’, you could call ‘*foo’.  Usually,
 this should not be necessary.  You can check what will be applied by the
 ‘which’ command:
 
      ~ $ which ls
      eshell/ls is a compiled Lisp function in `em-ls.el'
      ~ $ which *ls
      /bin/ls
 
    If you want to discard a given built-in command, you could declare an
 alias, Aliases.  Example:
 
      ~ $ which sudo
      eshell/sudo is a compiled Lisp function in `em-unix.el'
      ~ $ alias sudo '*sudo $*'
      ~ $ which sudo
      sudo is an alias, defined as "*sudo $*"
 
    If you would prefer to use the built-in commands instead of the
 external commands, set ‘eshell-prefer-lisp-functions’ to ‘t’.
 
    Some of the built-in commands have different behavior from their
 external counterparts, and some have no external counterpart.  Most of
 these will print a usage message when given the ‘--help’ option.
 
 ‘addpath’
      Adds a given path or set of paths to the PATH environment variable,
      or, with no arguments, prints the current paths in this variable.
 
 ‘alias’
      Define an alias (Aliases).  This does not add it to the
      aliases file.
 
 ‘clear’
      Scrolls the contents of the eshell window out of sight, leaving a
      blank window.  If provided with an optional non-nil argument, the
      scrollback contents are cleared instead.
 
 ‘date’
      Similar to, but slightly different from, the GNU Coreutils ‘date’
      command.
 
 ‘define’
      Define a varalias.  (elisp)Variable Aliases.
 
 ‘diff’
      Use Emacs’s internal ‘diff’ (not to be confused with ‘ediff’).
      (emacs)Comparing Files.
 
 ‘grep’
 ‘agrep’
 ‘egrep’
 ‘fgrep’
 ‘glimpse’
      The ‘grep’ commands are compatible with GNU ‘grep’, but use Emacs’s
      internal ‘grep’ instead.
 
 ‘info’
      Same as the external ‘info’ command, but uses Emacs’s internal Info
      reader.
 
 ‘jobs’
      List subprocesses of the Emacs process, if any, using the function
      ‘list-processes’.
 
 ‘kill’
      Kill processes.  Takes a PID or a process object and an optional
      signal specifier.
 
 ‘listify’
      Eshell version of ‘list’.  Allows you to create a list using Eshell
      syntax, rather than Elisp syntax.  For example, ‘listify foo bar’
      and ‘("foo" "bar")’ both evaluate to ‘("foo" "bar")’.
 
 ‘locate’
      Alias to Emacs’s ‘locate’ function, which simply runs the external
      ‘locate’ command and parses the results.  (emacs)Dired and
      Find.
 
 ‘make’
      Run ‘make’ through ‘compile’.  (emacs)Compilation.
 
 ‘occur’
      Alias to Emacs’s ‘occur’.  (emacs)Other Repeating Search.
 
 ‘printnl’
      Print the arguments separated by newlines.
 
 ‘cd’
      This command changes the current working directory.  Usually, it is
      invoked as ‘cd foo’ where ‘foo’ is the new working directory.  But
      ‘cd’ knows about a few special arguments:
 
      When it receives no argument at all, it changes to the home
      directory.
 
      Giving the command ‘cd -’ changes back to the previous working
      directory (this is the same as ‘cd $-’).
 
      The command ‘cd =’ shows the directory stack.  Each line is
      numbered.
 
      With ‘cd =foo’, Eshell searches the directory stack for a directory
      matching the regular expression ‘foo’ and changes to that
      directory.
 
      With ‘cd -42’, you can access the directory stack by number.
 
 ‘su’
 ‘sudo’
      Uses TRAMP’s ‘su’ or ‘sudo’ method (tramp)Inline methods to
      run a command via ‘su’ or ‘sudo’.  These commands are in the
      eshell-tramp module, which is disabled by default.
 
 2.3.1 Built-in variables
 ------------------------
 
 Eshell knows a few built-in variables:
 
 ‘$+’
      This variable always contains the current working directory.
 
 ‘$-’
      This variable always contains the previous working directory (the
      current working directory from before the last ‘cd’ command).
 
 ‘$_’
      It refers to the last argument of the last command.
 
 ‘$$’
      This is the result of the last command.  In case of an external
      command, it is ‘t’ or ‘nil’.
 
 ‘$?’
      This variable contains the exit code of the last command (0 or 1
      for Lisp functions, based on successful completion).
 

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