Provided by: opam-doc_2.0.5-1ubuntu1_all 
NAME
opam-var - Prints the value associated with a given variable
SYNOPSIS
opam var [OPTION]... [VAR]
DESCRIPTION
With a VAR argument, prints the value associated with VAR. Without argument, lists the
opam variables currently defined. This command is a shortcut to `opam config var` and
`opam config list`.
OPTIONS
--package=PACKAGE
List all variables defined for the given package
COMMON OPTIONS
These options are common to all commands.
--best-effort
Don't fail if all requested packages can't be installed: try to install as many as
possible. Note that not all external solvers may support this option (recent versions
of aspcud or mccs should). This is equivalent to setting $OPAMBESTEFFORT environment
variable.
--color=WHEN
Colorize the output. WHEN must be one of `always', `never' or `auto'.
--criteria=CRITERIA
Specify user preferences for dependency solving for this run. Overrides both
$OPAMCRITERIA and $OPAMUPGRADECRITERIA. For details on the supported language, and the
external solvers available, see http://opam.ocaml.org/doc/External_solvers.html. A
general guide to using solver preferences can be found at
http://www.dicosmo.org/Articles/usercriteria.pdf.
--cudf=FILENAME
Debug option: Save the CUDF requests sent to the solver to FILENAME-<n>.cudf.
--debug
Print debug message to stderr. This is equivalent to setting $OPAMDEBUG to "true".
--debug-level=LEVEL
Like --debug, but allows specifying the debug level (--debug sets it to 1). Equivalent
to setting $OPAMDEBUG to a positive integer.
--git-version
Print the git version of opam, if set (i.e. you are using a development version), and
exit.
--help[=FMT] (default=auto)
Show this help in format FMT. The value FMT must be one of `auto', `pager', `groff' or
`plain'. With `auto', the format is `pager` or `plain' whenever the TERM env var is
`dumb' or undefined.
--ignore-pin-depends
Ignore extra pins required by packages that get pinned, either manually through opam
pin or through opam install DIR. This is equivalent to setting IGNOREPINDEPENDS=true.
--json=FILENAME
Save the results of the opam run in a computer-readable file. If the filename contains
the character `%', it will be replaced by an index that doesn't overwrite an existing
file. Similar to setting the $OPAMJSON variable.
--no-aspcud
Deprecated.
--no-auto-upgrade
When configuring or updating a repository that is written for an earlier opam version
(1.2), opam internally converts it to the current format. This disables this
behaviour. Note that repositories should define their format version in a 'repo' file
at their root, or they will be assumed to be in the older format. It is, in any case,
preferable to upgrade the repositories manually using opam admin upgrade [--mirror
URL] when possible.
--no-self-upgrade
Opam will replace itself with a newer binary found at OPAMROOT/opam if present. This
disables this behaviour.
-q, --quiet
Disables --verbose.
--root=ROOT
Use ROOT as the current root path. This is equivalent to setting $OPAMROOT to ROOT.
--safe, --readonly
Make sure nothing will be automatically updated or rewritten. Useful for calling from
completion scripts, for example. Will fail whenever such an operation is needed ; also
avoids waiting for locks, skips interactive questions and overrides the $OPAMDEBUG
variable. This is equivalent to set environment variable $OPAMSAFE.
--solver=CMD
Specify the CUDF solver to use for resolving package installation problems. This is
either a predefined solver (this version of opam supports builtin-mccs+lp(),
builtin-mccs+glpk, aspcud, mccs, aspcud-old, packup), or a custom command that should
contain the variables %{input}%, %{output}%, %{criteria}%, and optionally %{timeout}%.
This is equivalent to setting $OPAMEXTERNALSOLVER.
--strict
Fail whenever an error is found in a package definition or a configuration file. The
default is to continue silently if possible.
--switch=SWITCH
Use SWITCH as the current compiler switch. This is equivalent to setting $OPAMSWITCH
to SWITCH.
--use-internal-solver
Disable any external solver, and use the built-in one (this requires that opam has
been compiled with a built-in solver). This is equivalent to setting $OPAMNOASPCUD or
$OPAMUSEINTERNALSOLVER.
-v, --verbose
Be more verbose. One -v shows all package commands, repeat to also display commands
called internally (e.g. tar, curl, patch etc.) Repeating n times is equivalent to
setting $OPAMVERBOSE to "n".
--version
Show version information.
-w, --working-dir
Whenever updating packages that are bound to a local, version-controlled directory,
update to the current working state of their source instead of the last committed
state, or the ref they are pointing to. This only affects packages explicitly listed
on the command-line.It can also be set with $OPAMWORKINGDIR.
-y, --yes
Answer yes to all yes/no questions without prompting. This is equivalent to setting
$OPAMYES to "true".
ENVIRONMENT VARIABLES
Opam makes use of the environment variables listed here. Boolean variables should be set
to "0", "no", "false" or the empty string to disable, "1", "yes" or "true" to enable.
OPAMALLPARENS surround all filters with parenthesis
OPAMAUTOREMOVE see remove option `--auto-remove`
OPAMBESTEFFORT see option `--best-effort`
OPAMBESTEFFORTPREFIXCRITERIA sets the string that must be prepended to the criteria when
the `--best-effort` option is set, and is expected to maximise the `opam-query` property
in the solution
OPAMCOLOR, when set to always or never, sets a default value for the --color option.
OPAMCRITERIA specifies user preferences for dependency solving. The default value depends
on the solver version, use `config report` to know the current setting. See also option
--criteria
OPAMCUDFFILE file save the cudf graph to file-actions-explicit.dot
OPAMCURL can be used to select a given 'curl' program. See OPAMFETCH for more options.
OPAMDEBUG see options `--debug' and `--debug-level'.
OPAMDOWNLOADJOBS sets the maximum number of simultaneous downloads.
OPAMDRYRUN see option `--dry-run`
OPAMEDITOR sets the editor to use for opam file editing, overrides $EDITOR and $VISUAL
OPAMERRLOGLEN sets the number of log lines printed when a sub-process fails. 0 to print
all.
OPAMEXTERNALSOLVER see option `--solver'.
OPAMFAKE see option `--fake`
OPAMFETCH specifies how to download files: either `wget', `curl' or a custom command where
variables %{url}%, %{out}%, %{retry}%, %{compress}% and %{checksum}% will be replaced.
Overrides the 'download-command' value from the main config file.
OPAMFIXUPCRITERIA same as OPAMUPGRADECRITERIA, but specific to fixup
OPAMIGNORECONSTRAINTS see install option `--ignore-constraints-on`
OPAMIGNOREPINDEPENDS see option `--ignore-pin-depends`
OPAMJOBS sets the maximum number of parallel workers to run.
OPAMJSON log json output to the given file (use character `%' to index the files)
OPAMLOCKED see install option `--locked`
OPAMLOGS logdir sets log directory, default is a temporary directory in /tmp
OPAMMAKECMD set the system make command to use
OPAMNOAUTOUPGRADE disables automatic internal upgrade of repositories in an earlier format
to the current one, on 'update' or 'init'.
OPAMKEEPLOGS tells opam to not remove some temporary command logs and some backups. This
skips some finalisers and may also help to get more reliable backtraces
OPAMLOCKRETRIES sets the number of tries after which opam gives up acquiring its lock and
fails. <= 0 means infinite wait.
OPAMMERGEOUT merge process outputs, stderr on stdout
OPAMNO answer no to any question asked.
OPAMNOASPCUD Deprecated.
OPAMNOCHECKSUMS enables option --no-checksums when available.
OPAMNOSELFUPGRADE see option `--no-self-upgrade'.
OPAMPINKINDAUTO sets whether version control systems should be detected when pinning to a
local path. Enabled by default since 1.3.0.
OPAMPRECISETRACKING fine grain tracking of directories
OPAMREQUIRECHECKSUMS Enables option `--require-checksums' when available (e.g. for `opam
install`).
OPAMRETRES sets the number of tries before failing downloads.
OPAMROOT see option `--root'. This is automatically set by `opam env --root=DIR
--set-root'.
OPAMROOTISOK don't complain when running as root.
OPAMSAFE see option `--safe'
OPAMSHOW see option `--show`
OPAMSKIPUPDATE see option `--skip-updates`
OPAMSKIPVERSIONCHECKS bypasses some version checks. Unsafe, for compatibility testing
only.
OPAMSOLVERTIMEOUT change the time allowance of the solver. Default is 60.0, set to 0 for
unlimited. Note that all solvers may not support this option.
OPAMSTATUSLINE display a dynamic status line showing what's currently going on on the
terminal. (one of one of `always', `never' or `auto')
OPAMSTATS display stats at the end of command
OPAMSTRICT fail on inconsistencies (file reading, switch import, etc.)
OPAMSWITCH see option `--switch'. Automatically set by `opam env --switch=SWITCH
--set-switch'.
OPAMUNLOCKBASE see install option `--unlock-base`
OPAMUPGRADECRITERIA specifies user preferences for dependency solving when performing an
upgrade. Overrides OPAMCRITERIA in upgrades if both are set. See also option --criteria
OPAMUSEINTERNALSOLVER see option `--use-internal-solver'.
OPAMUSEOPENSSL force openssl use for hash computing
OPAMUTF8 use UTF8 characters in output (one of one of `always', `never' or `auto'). By
default `auto', which is determined from the locale).
OPAMUTF8MSGS use extended UTF8 characters (camels) in opam messages. Implies OPAMUTF8.
This is set by default on OSX only.
OPAMVALIDATIONHOOK hook if set, uses the `%{hook%}` command to validate an opam repository
update
OPAMVAR_var overrides the contents of the variable var when substituting `%{var}%` strings
in `opam` files.
OPAMVAR_package_var overrides the contents of the variable package:var when substituting
`%{package:var}%` strings in `opam` files.
OPAMVERBOSE see option `--verbose'.
OPAMWORKINGDIR see option `--working-dir`
OPAMYES see option `--yes'.
EXIT STATUS
As an exception to the following, the `exec' command returns 127 if the command was not
found or couldn't be executed, and the command's exit value otherwise.
0 Success, or true for boolean queries.
1 False. Returned when a boolean return value is expected, e.g. when running with
--check, or for queries like opam lint.
2 Bad command-line arguments, or command-line arguments pointing to an invalid context
(e.g. file not following the expected format).
5 Not found. You requested something (package, version, repository, etc.) that couldn't
be found.
10 Aborted. The operation required confirmation, which wasn't given.
15 Could not acquire the locks required for the operation.
20 There is no solution to the user request. This can be caused by asking to install two
incompatible packages, for example.
30 Error in package definition, or other metadata files. Using --strict raises this error
more often.
31 Package script error. Some package operations were unsuccessful. This may be an error
in the packages or an incompatibility with your system. This can be a partial error.
40 Sync error. Could not fetch some remotes from the network. This can be a partial
error.
50 Configuration error. Opam or system configuration doesn't allow operation, and needs
fixing.
60 Solver failure. The solver failed to return a sound answer. It can be due to a broken
external solver, or an error in solver configuration.
99 Internal error. Something went wrong, likely due to a bug in opam itself.
130 User interrupt. SIGINT was received, generally due to the user pressing Ctrl-C.
FURTHER DOCUMENTATION
See https://opam.ocaml.org/doc.
AUTHORS
Vincent Bernardoff <vb@luminar.eu.org>
Raja Boujbel <raja.boujbel@ocamlpro.com>
Roberto Di Cosmo <roberto@dicosmo.org>
Thomas Gazagnaire <thomas@gazagnaire.org>
Louis Gesbert <louis.gesbert@ocamlpro.com>
Fabrice Le Fessant <Fabrice.Le_fessant@inria.fr>
Anil Madhavapeddy <anil@recoil.org>
Guillem Rieu <guillem.rieu@ocamlpro.com>
Ralf Treinen <ralf.treinen@pps.jussieu.fr>
Frederic Tuong <tuong@users.gforge.inria.fr>
BUGS
Check bug reports at https://github.com/ocaml/opam/issues.