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Special Variables

This chapter in the Oils Reference describes special variables for OSH and YSH.

YSH Vars

ARGV

Replacement for "$@"

ENV

TODO

_this_dir

The directory the current script resides in. This knows about 3 situations:

• The location of oshrc in an interactive shell
• The location of the main script, e.g. in osh myscript.sh
• The location of script loaded with the source builtin

It's useful for "relative imports".

YSH Status

_status

An Int that's set by the try builtin.

try {
  ls /bad  # exits with status 2
}
if (_status !== 0) {  # _status is 2
  echo 'failed'
}

_error

A Dict that's set by the try builtin when catching certain errors.

Such errors include JSON/J8 encoding/decoding errors, and user errors from the error builtin.

try {
  echo $[toJson( /d+/ )]  # invalid Eggex type
}
echo "failed: $[_error.message]"  # => failed: Can't serialize ...

_pipeline_status

Alias for PIPESTATUS.

_process_sub_status

The exit status of all the process subs in the last command.

YSH Tracing

SHX_indent

SHX_punct

SHX_pid_str

YSH Read

_reply

YSH read sets this variable:

read --all < myfile
echo $_reply

Oils VM

OILS_VERSION

The version of Oils that's being run, e.g. 0.9.0.

OILS_GC_THRESHOLD

At a GC point, if there are more than this number of live objects, collect garbage.

OILS_GC_ON_EXIT

Set OILS_GC_ON_EXIT=1 to explicitly collect and free() before the process exits. By default, we let the OS clean up.

Useful for ASAN testing.

OILS_GC_STATS

When the shell process exists, print GC stats to stderr.

OILS_GC_STATS_FD

When the shell process exists, print GC stats to this file descriptor.

Shell Vars

IFS

Used for word splitting. And the builtin shSplit() function.

LANG

TODO: bash compat

GLOBIGNORE

TODO: bash compat

Shell Options

SHELLOPTS

bash compat: serialized options for the set builtin.

BASHOPTS

bash compat: serialized options for the shopt builtin.

Other Env

HOME

$HOME is used for:

1. ~ expansion
2. ~ abbreviation in the UI (the dirs builtin, \W in $PS1).

Note: The shell doesn't set $HOME. According to POSIX, the program that invokes the login shell sets it based on /etc/passwd.

PATH

A colon-separated string that's used to find executables to run.

POSIX Special

Other Special

BASH_REMATCH

Result of regex evaluation [[ $x =~ $pat ]].

PIPESTATUS

Exit code of each element in a pipeline.

Call Stack

Tracing

LINENO

Process State

BASHPID

TODO

PPID

TODO

UID

EUID

Process Stack

Shell State

Completion

COMP_WORDS

An array of words, split by : and = for compatibility with bash. New completion scripts should use COMP_ARGV instead.

COMP_CWORD

Discouraged; for compatibility with bash.

COMP_LINE

Discouraged; for compatibility with bash.

COMP_POINT

Discouraged; for compatibility with bash.

COMPREPLY

User-defined completion functions should Fill this array with candidates. It is cleared on every completion request.

COMP_ARGV

An array of partial command arguments to complete. Preferred over COMP_WORDS. The compadjust builtin uses this variable.

(An OSH extension to bash.)

History

HISTFILE

Override the default OSH history location.

YSH_HISTFILE

Override the default YSH history location.

cd

PWD

OLDPWD

CDPATH

getopts

OPTIND

OPTARG

OPTERR

read

REPLY

OSH read sets this:

read < myfile

Functions

RANDOM

bash compat

SECONDS

bash compat