opam-var - (unknown subject)



opam-var - Display and update the value associated with a given variable


opam var [OPTION]... [VAR[=[VALUE]]]


Without argument, lists the opam variables currently defined. With a VAR argument, prints the value associated with VAR. Otherwise, sets or updates VAR's value. If no scope is given, it acts on switch variables by default. This command does not perform any variable expansion.



If only VAR is given, displays its associated value. If VALUE is absent, VAR's value is removed. Otherwise, its value is overwritten.



Act on global configuration


Answer no to all opam yes/no questions without prompting. See also --confirm-level. This is equivalent to setting $OPAMNO to "true".


List all variables defined for the given package

-y, --yes

Answer yes to all opam yes/no questions without prompting. See also --confirm-level. This is equivalent to setting $OPAMYES to "true".


These options are common to all commands.

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.

--cli=MAJOR.MINOR (absent=2.1)

Use the command-line interface syntax and semantics of MAJOR.MINOR. Intended for any persistent use of opam (scripts, blog posts, etc.), any version of opam in the same MAJOR series will behave as for the specified MINOR release. The flag was not available in opam 2.0, so to select the 2.0 CLI, set the OPAMCLI environment variable to 2.0 instead of using this parameter.


Colorize the output. WHEN must be one of ‘always', ‘never' or ‘auto'.


Confirmation level, LEVEL must be one of ‘ask', ‘no', ‘yes' or ‘unsafe-yes'. Can be specified more than once. If --yes or --no are also given, the value of the last --confirm-level is taken into account. This is equivalent to setting $OPAMCONFIRMLEVEL‘.


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.


Debug option: Save the CUDF requests sent to the solver to FILENAME-<n>.cudf.


Print debug message to stderr. This is equivalent to setting $OPAMDEBUG to "true".


Like --debug, but allows specifying the debug level (--debug sets it to 1). Equivalent to setting $OPAMDEBUG to a positive integer.


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 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.


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.


Removed in 2.1.


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.


Opam will replace itself with a newer binary found at OPAMROOT/opam if present. This disables this behaviour.

-q, --quiet

Disables --verbose.


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.


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, builtin-dummy-z3-solver, builtin-dummy-0install-solver, 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.


Fail whenever an error is found in a package definition or a configuration file. The default is to continue silently if possible.


Use SWITCH as the current compiler switch. This is equivalent to setting $OPAMSWITCH to SWITCH.


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".


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. As source directory is copied as it is, if it isn't clean it may result on a opam build failure.This only affects packages explicitly listed on the command-line.It can also be set with $OPAMWORKINGDIR.


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.

OPAMASSUMEDEPEXTS see option ‘--assume-depexts'.

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.

OPAMBUILDDOC Removed in 2.1.

OPAMBUILDTEST Removed in 2.1.

OPAMCLI see option ‘--cli'.

OPAMCOLOR when set to always or never, sets a default value for the ‘--color' option.

OPAMCONFIRMLEVEL see option ‘--confirm-level‘. OPAMCONFIRMLEVEL has priority over OPAMYES and OPAMNO.

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 save the cudf graph to file-actions-explicit.dot.

OPAMCUDFTRIM controls the filtering of unrelated packages during CUDF preprocessing.

OPAMCURL can be used to select a given 'curl' program. See OPAMFETCH for more options.

OPAMDEBUG see options ‘--debug' and ‘--debug-level'.

OPAMDEBUGSECTIONS if set, limits debug messages to the space-separated list of sections. Sections can optionally have a specific debug level (for example, CLIENT:2 or CLIENT CUDF:2), but otherwise use ‘--debug-level'.

OPAMDIGDEPTH defines how aggressive the lookup for conflicts during CUDF preprocessing is.

OPAMDOWNLOADJOBS sets the maximum number of simultaneous downloads.

OPAMDROPWORKINGDIR overrides packages previously updated with --working-dir on update. Without this variable set, opam would keep them unchanged unless explicitly named on the command-line.

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.


OPAMIGNORECONSTRAINTS see install option ‘--ignore-constraints-on'.

OPAMIGNOREPINDEPENDS see option ‘--ignore-pin-depends'.

OPAMINPLACEBUILD see option ‘--inplace-build'.

OPAMJOBS sets the maximum number of parallel workers to run.

OPAMJSON log json output to the given file (use character ‘%' to index the files).

OPAMKEEPBUILDDIR see install option ‘--keep-build-dir'.

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.

OPAMLOCKED combination of ‘--locked' and ‘--lock-suffix' options.

OPAMLOGS logdir sets log directory, default is a temporary directory in /tmp

OPAMMAKECMD set the system make command to use.

OPAMMERGEOUT merge process outputs, stderr on stdout.

OPAMNO answer no to any question asked, see options ‘--no‘ and ‘--confirm-level‘. OPAMNO is ignored if either OPAMCONFIRMLEVEL or OPAMYES is set.

OPAMNOAGGREGATE with ‘opam admin check', don't aggregate packages.


OPAMNOAUTOUPGRADE disables automatic internal upgrade of repositories in an earlier format to the current one, on 'update' or 'init'.

OPAMNOCHECKSUMS enables option --no-checksums when available.

OPAMNODEPEXTS disables system dependencies handling, see option ‘--no-depexts'.


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.

OPAMPREPRO set this to false to disable CUDF preprocessing. Less efficient, but might help debugging solver issue.

OPAMREQUIRECHECKSUMS Enables option ‘--require-checksums' when available (e.g. for ‘opam install').

OPAMRETRIES sets the number of tries before failing downloads.

OPAMREUSEBUILDDIR see option ‘--reuse-build-dir'.

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.

OPAMSOLVERALLOWSUBOPTIMAL (default ‘true') allows some solvers to still return a solution when they reach timeout; while the solution remains assured to be consistent, there is no guarantee in this case that it fits the expected optimisation criteria. If ‘true', opam willcontinue with a warning, if ‘false' a timeout is an error. Currently only the builtin-z3 backend handles this degraded case.

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.

OPAMSTATS display stats at the end of command.

OPAMSTATUSLINE display a dynamic status line showing what's currently going on on the terminal. (one of one of ‘always', ‘never' or ‘auto')

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 if set, uses the ‘%{hook%}' command to validate an opam repository update.

OPAMVERBOSE see option ‘--verbose'.


OPAMWITHDOC see install option ‘--with-doc'.

OPAMWITHTEST see install option ‘--with-test.

OPAMWORKINGDIR see option ‘--working-dir'.

OPAMYES see options ‘--yes' and ‘--confirm-level‘. OPAMYES has has priority over OPAMNO and is ignored if OPAMCONFIRMLEVEL is set.

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.


All scripts and programmatic invocations of opam should use ‘--cli' in order to ensure that they work seamlessly with future versions of the opam client. Additionally, blog posts or other documentation can benefit, as it prevents information from becoming stale.

Although opam only supports roots (˜/.opam/) for the current version, it does provide backwards compatibility for its command-line interface.

Since CLI version support was only added in opam 2.1, use OPAMCLI to select 2.0 support (as opam 2.0 will just ignore it), and ‘--cli=2.1' for 2.1 (or later) versions, since an environment variable controlling the parsing of syntax is brittle. To this end, opam displays a warning if OPAMCLI specifies a valid version other than 2.0, and also if ‘--cli=2.0' is specified.

The command-line version is selected by using the ‘--cli' option or the OPAMCLI environment variable. ‘--cli' may be specified morethan once, where the last instance takes precedence. OPAMCLI is only inspected if ‘--cli' is not given.


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.


Success, or true for boolean queries.


False. Returned when a boolean return value is expected, e.g. when running with --check, or for queries like opam lint.


Bad command-line arguments, or command-line arguments pointing to an invalid context (e.g. file not following the expected format).


Not found. You requested something (package, version, repository, etc.) that couldn't be found.


Aborted. The operation required confirmation, which wasn't given.


Could not acquire the locks required for the operation.


There is no solution to the user request. This can be caused by asking to install two incompatible packages, for example.


Error in package definition, or other metadata files. Using --strict raises this error more often.


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.


Sync error. Could not fetch some remotes from the network. This can be a partial error.


Configuration error. Opam or system configuration doesn't allow operation, and needs fixing.


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.


Internal error. Something went wrong, likely due to a bug in opam itself.


User interrupt. SIGINT was received, generally due to the user pressing Ctrl-C.


See https://opam.ocaml.org/doc.


Vincent Bernardoff <[email protected]>
Raja Boujbel <[email protected]>
Roberto Di Cosmo <[email protected]>
Thomas Gazagnaire <[email protected]>
Louis Gesbert <[email protected]>
Fabrice Le Fessant <[email protected]>
Anil Madhavapeddy <[email protected]>
Guillem Rieu <[email protected]>
Ralf Treinen <[email protected]>
Frederic Tuong <[email protected]>


Check bug reports at https://github.com/ocaml/opam/issues.

Updated 2024-01-29 - jenkler.se | uex.se