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Joel Berger


zoidbuiltins - Zoidberg's builtins


This is a listing of the default builtins of the Zoidberg shell. Many of these are defined in the default plugins, so a modified shell can have different builtin commands.


alias name
alias name=command
alias name command

Make name an alias to command. Aliases work like macros in the shell, this means they are substituted before the commnd code is interpreted and can contain complex statements.

Without command shows the alias defined for name if any; without arguments lists all aliases that are currently defined.

Aliases are simple substitutions at the start of a command string. If you want something more intelligent like interpolating arguments into a string define a builtin command; see hash.

bg job_spec

Run the job corresponding to jobspec as an asynchronous background process.

Without argument uses the "current" job.

cd [-v|--verbose] [dir|-|(+|-)hist_number]
cd (-l|--list)

Changes the current working directory to dir. When used with a single dash changes to OLDPWD.

This command uses the environment variable 'CDPATH'. It serves as a search path when the directory you want to change to isn't found in the current directory.

This command also uses a directory history. The '-number' and '+number' switches are used to change directory to an positive or negative offset in this history.


Output the current dir stack.

TODO some options

Note that the dir stack is ont related to the dir history. It was only implemented because historic implementations have it.



eval cmd

Eval cmd like a shell command. Main use of this is to run code stored in variables.

exec cmd

Execute cmd. This effectively ends the shell session, process flow will NOT return to the prompt.

export var=value

Set the environment variable var to value.

TODO explain how export moved varraibles between the perl namespace and the environment


A command that always returns an error without doing anything.

fc [-r][-e editor] [first [last]]
fc -l [-nr] [first [last]]
fc -s [old=new] [first [last]]

"Fix command", this builtin allows you to edit and re-execute commands from the history. first and last are either command numbers or strings matching the beginning of a command; a negative number is used to designate commands by counting back from the current one. Use the '-l' option to list the commands in the history, and the '-n' switch to surpress the command numbers in the listing.The '-r' switch reverses the order of the commands. The '-s' switch re-executes the commands without editing.

first and last default to '-16' and '-1' when the '-l' option is given. Otherwise first defaults to '-1' and last defaults to first.

Note that the selection of the editor is not POSIX compliant but follows bash, if no editor is given using the '-e' option the environment variables 'FCEDIT' and 'EDITOR' are both checked, if neither is set, vi is used. ( According to POSIX we should use 'ed' by default and probably ignore the 'EDITOR' varaiable, but I don't think that is "What You Want" )

Following zsh setting the editor to '-' is identical with using the -s switch.

Also note that fc removes itself from the history and adds the resulting command instead.

Typically r is aliased to 'fc -s' so r will re-execute the last command, optionally followed by a substitution and/or a string to match the begin of the command.

TODO: regex/glob substitution for '-s' switch; now only does string substitution.

fg job_spec

Run the job corresponding to jobspec as a foreground process.

Without argument uses the "current" job.


Returns the commandline history either as an array reference or as an array.

This routine does not use the history file.

hash location
hash -r


Command to manipulate the commands hash and command lookup logic.

help [topic|command command]

Prints out a help text.

history [--type type] [--read] [-n|--nonu] [-r|--reverse] [first [last]]

Returns (a part of) the history. By default it tries to find the commandline history (depending on GetHistory), but the '--read' option forces reading the history file. To get other log types, like 'pwd', use the '--type' option. The '--nonu' option surpressees line numbering for the terminal output.

The arguments first and last can either be a positive or negative integer, representing the command number or reverse offset, or a string matching the begin of the command. If only one integer is given last defaults to '-1'; if only one string is given last defaults to first. As a bonus you can supply a regex reference instead of a string when using the perl interface.

Note that unlike fc the history command is not specified by posix and the implementation varies widely for different shells. In zoid, fc is build on top of history, so options for history are chosen consistently with fc.

jobs [-l,--list|-p,--pgids] job_spec ...

Lists current jobs.

If job specs are given as arguments only lists those jobs.

The --pgids option only lists the process group ids for the jobs without additional information.

The --list option gives more verbose output, it adds the process group id of the job and also shows the stack of commands pending for this job.

This command is not POSIX compliant. It uses '-l' in a more verbose way then specified by POSIX. If you wat to make sure you have POSIX compliant verbose output try: jobs -l | {! /^\t/}g.

kill -l
kill [-w | -s sigspec|-n signum|-sigspec] (pid|job_spec)

Sends a signal to a process or a process group. By default the "TERM" signal is used.

The '-l' option list all possible signals.

The -w or --wipe option is zoidberg specific. It not only kills the job, but also wipes the list that would be executed after the job ends.

log string type

Adds string to the history file with the current timestamp and the supplied type tag. The type defaults to "log". If the type is set to "hist" the entry will become part of the command history after the history file is read again.



popd dir

Pops a directory from the dir stack and cds to that directory.

TODO some options

pushd dir

Push dir on the dir stack.

TODO some options


Prints the current PWD.

read [-r] var1 var2 ..

Read a line from STDIN, split the line in words and assign the words to the named enironment variables. Remaining words are stored in the last variable.

Unless '-r' is specified the backslash is treated as an escape char and is it possible to escape the newline char.


Returns a line of input.

reload module [module, ..]
reload file [file, ..]

Force (re-)loading of a module file. Typically used for debugging modules, where you reload the module after each modification to test it interactively.

TODO: recursive switch that scans for 'use' statements


Given a list of items presents the user with a menu and returns the choice made or undef.

set [+-][abCefnmnuvx]
set [+o|-o] option

Set or unset a shell option. Although sometimes confusing a '+' switch unsets the option, while the '-' switch sets it.

Short options correspond to the following names:

        a  =>  allexport  *
        b  =>  notify
        C  =>  noclobber
        e  =>  errexit    *
        f  =>  noglob
        m  =>  monitor    *
        n  =>  noexec     *
        u  =>  nounset    *
        v  =>  verbose
        x  =>  xtrace     *
        *) Not yet supported by the rest of the shell

See zoiduser for a description what these and other options do.

FIXME takes also hash arguments

setenv var value

Like export, but with a slightly different syntax.


Takes either an array or an array reference and uses that as new commandline history.

This routine does not alter the history file.

source file

Run the perl script file. This script is NOT the same as the commandline syntax. Try using Zoidberg::Shell in these scripts.

symbols [-a|--all] [class]

Output a listing of symbols in the specified class. Class defaults to the current perl namespace, by default Zoidberg::Eval.

All symbols are prefixed by their sigil ('$', '@', '%', '&' or '*') where '*' is used for filehandles.

By default sub classes (hashes containing '::') and special symbols (symbols without letters in their name) are hidden. Use the --all switch to see these.


A command that never fails and does absolutely nothing.



unalias name

Remove an alias definition.

unsetenv var

Set var to undefined.



which [-a|--all|-m|--module] ITEM

Finds ITEM in PATH or INC if the -m or --module option was used. If the -a or --all option is used all it doesn't stop after the first match.

TODO it should identify aliases

TODO what should happen with contexts other then CMD ?


zoiduser(1), perl(1), http://github.com/jberger/Zoidberg