OPAM-VAR(1)

📦
version 2.6.1 · 8 versions
, in arch rolling, fedora 44

💅 OPAM-VAR(1) — Opam Manual, but make it bestie 🎀

ok so this is the page for opam-var, bestie, and honestly she's lowkey one of the most useful lil commands in the whole opam friend group. she reads variables, she writes variables, and she absolutely does NOT do expansion. periodt.

✨ NAME ✨

opam-var — display and update the value associated with a given variable 💖

🌈 SYNOPSIS 🌈

opam var [--global] [--package=PACKAGE] [OPTION]… [VAR[=[VALUE]]]

🦋 DESCRIPTION 🦋

ok so here's the vibe check 🌸

  • no argument at all → she lists all the opam variables that are currently defined. a lil inventory, a lil tour of your setup ✨
  • you hand her a VAR → she prints the value associated with that VAR 💖
  • anything else → she sets or updates VAR's value 🎀

If no scope is given, she acts on switch variables by default. main character energy honestly 💅

⚠️ okay this one matters: this command does not perform any variable expansion. like, none. zero. she shows you exactly what's there, no glow-up, no substitutions, no makeover montage 🙈

🌸 ARGUMENTS 🌸

  • VAR[=[VALUE]] — the whole menu, right here:
    • if you give her only VAR, she displays its associated value 👀
    • if VALUE is absent, then VAR's value gets removed. bye bestie 💀
    • otherwise, its value is overwritten ✨

💜 OPTIONS 💜

  • --global — act on global configuration. the whole entire world, not just your current switch 🌍👑
  • --package=PACKAGE — list all variables defined for the given package 📦. all of them. no crumbs.

👑 COMMON OPTIONS 👑

these are common to all commands — so they're basically the group chat that everyone's in. you already know 💅

  • --best-effort — don't fail if all the requested packages can't be installed: try to install as many as possible 🫶. ngl, not every external solver may support this (recent versions of aspcud or mccs should, so if you're on those you're chilling). this is equivalent to setting the $OPAMBESTEFFORT environment variable.
  • --cli=MAJOR.MINOR (absent=2.6) — use the command-line interface syntax and semantics of MAJOR.MINOR 🕰️. this is intended for any persistent use of opam (scripts, blog posts, etc.), and any version of opam in the same MAJOR series will behave as for the specified MINOR release. heads up though: the flag wasn't 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 🙈
  • --color=WHEN — colorize the output 🎨. WHEN must be one of always, never or auto.
  • --confirm-level=LEVEL — 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` .
  • --criteria=CRITERIA — specify your user preferences for dependency solving for this run 👑. overrides $OPAMCRITERIA, $OPAMFIXUPCRITERIA 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 where <n> is the n-th call to the solver during the opam run.
  • --debug — print debug messages to stderr 🔍. this is equivalent to setting $OPAMDEBUG to "true".
  • --debug-level=LEVEL — like --debug, but lets you specify 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 it's set (i.e. you're 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 — answer no to all opam yes/no questions without prompting 🙅. see also --confirm-level. this is equivalent to setting $OPAMNO to "true".
  • --no-aspcud — removed in 2.1 💀 (she's gone bestie, no notes)
  • --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 that 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 that 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, builtin-dummy-z3-solver, builtin-0install, 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 👩‍💻. as the 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.
  • -y, --yes — answer yes to all opam yes/no questions without prompting ✅. see also --confirm-level. this is equivalent to setting $OPAMYES to "true".

ok that's the crew so far bestie, but there's more where that came from… keep scrolling, we're not done yet 💖

🫶 ENVIRONMENT 🫶

okay bestie, so opam is obsessed with environment variables and honestly? same. here's the whole list, no cap 💅

quick vibe check on booleans first: these lil guys love a yes/no moment. set them to "0", "no", "false" or the empty string to disable 💀, and to "1", "yes" or "true" to enable ✨. that's it, that's the whole system.

  • OPAMALLPARENS — wraps all the filters in parentheses 🎀
  • OPAMASSUMEDEPEXTS — go look at the --assume-depexts option, she spills the tea there 💖
  • OPAMAUTOANSWER — internal use only, bestie. nothing to see here 🙈
  • OPAMAUTOREMOVE — see the remove option --auto-remove 🧚
  • OPAMBESTEFFORT — see option --best-effort 💪
  • OPAMBESTEFFORTPREFIXCRITERIA — sets the string that must be prepended to the criteria whenever the --best-effort option is on, and it's expected to maximise the opam-query property in the solution 📈
  • OPAMBUILDDOC — Removed in 2.1 💀 she's gone girl
  • OPAMBUILDTEST — Removed in 2.1 💀 also gone
  • OPAMCLI — see option --cli 🖥️
  • OPAMCOLOR — when you set it to always or never, it sets a default value for the --color option 🌈
  • OPAMCONFIRMLEVEL — see option --confirm-level. and heads up: OPAMCONFIRMLEVEL has priority over OPAMYES and OPAMNO 👑 she's the main character here
  • OPAMCRITERIA — specifies your user preferences for dependency solving ✨ the default value depends on the solver version, so run 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 — use this to select a given curl program 🌀 see OPAMFETCH for more options
  • OPAMDEBUG — see options --debug and --debug-level 🐛
  • OPAMDEBUGSECTIONS — if set, it 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, and it overrides $EDITOR and $VISUAL 📝
  • OPAMERRLOGLEN — sets the number of log lines printed when a sub-process fails 😭 set it to 0 to print all of them
  • 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 and reinstall 🛠️
  • OPAMIGNOREAVAILABLE — see the install option --ignore-available-on 👀
  • OPAMIGNORECONSTRAINTS — see the 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 the 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 — a combination of the --locked and --lock-suffix options 🔒
  • OPAMLOGS — logdir sets the 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 🧺
  • OPAMNOASPCUD — Deprecated ⚠️
  • 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 🚫
  • OPAMNOENVNOTICE — Internal 🤫
  • 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
  • OPAMREPOSITORYTARRING — internally store all non-vcs repositories as tar.gz files (by default, http repositories are stored as archive) 🗜️ this can be much faster on filesystems that don't cope well with scanning large trees. all operation are done in-memory, no I/O for scanning the repository
  • 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 will continue 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
  • OPAMSOLVERTOLERANCE — changes the tolerance towards the solver choosing an unoptimized solution (i.e. might pull outdated packages) 📉 typical values range from 0.0 (best solution known to the solver) to 1.0 (unoptimized solution). default is 0.0. this option is useful in case the solver can't find a solution in a reasonable time (see $OPAMSOLVERTIMEOUT). note that all solvers may not support this option
  • OPAMSTATS — Removed in 2.4 💀
  • OPAMSTATUSLINE — display a dynamic status line showing what's currently going on on the terminal 📺 (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 the 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 — Removed in 2.2 💀
  • OPAMUTF8 — use UTF8 characters in output 🦋 (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 macOS only 🍎
  • OPAMVALIDATIONHOOK — if set, uses the %{hook}% command to validate an opam repository update 🪝
  • OPAMVERBOSE — see option --verbose 🗣️
  • OPAMVERBOSEON — see option --verbose-on 📢
  • OPAMVERSIONLAGPOWER — do not use 🙈
  • OPAMWITHDEVSETUP — see the install option --with-dev-setup 🧑‍💻
  • OPAMWITHDOC — see the install option --with-doc 📚
  • OPAMWITHTEST — see the install option --with-test 🧪
  • OPAMWORKINGDIR — see option --working-dir 📂
  • OPAMYES — see options --yes and --confirm-level 🫡 OPAMYES 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 🔤

🌈 CLI VERSION 🌈

okay so this part is important and i need you to actually listen bestie 🫶

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 📰 like, future-proofing your whole brand.

although opam only supports roots (~/.opam/) for the current version, it does provide backwards compatibility for its command-line interface 🫡 so nobody gets left behind.

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 more than once, where the last instance takes precedence 👑 OPAMCLI is only inspected if --cli is not given. periodt 💅

💀 EXIT STATUS 💀

ok so bestie, real talk: opam tells you what happened through its exit code, and you need to know this because scripts check it. One gloriously chaotic exception first though:

EXCEPTION ALERT — the exec command does NOT play by the rules below. It returns 127 if the command wasn't found or couldn't be executed, and otherwise it just hands you the command's own exit value. That's it. That's the whole deal. 💅

Now, the main character list:

  • 0 — Success! ✨ Or true for boolean queries. We love a happy ending.
  • 1 — False. It's returned when a boolean return value is expected, like when you run with --check, or for queries like opam lint. So like, "no 💖" not "oops 😭".
  • 2 — Bad command-line arguments, or arguments pointing at an invalid context (for example, a file that doesn't follow the expected format). Basically you typed something cursed.
  • 5 — Not found. You asked for something (a package, a version, a repository, etc.) and it simply... wasn't there. 🫥
  • 10 — Aborted. The operation needed confirmation and you didn't give it. No consent, no operation, periodt.
  • 15 — Could not acquire the locks required for the operation. Somebody else is holding the door. 🚪
  • 20 — There is no solution to the user request. Classic cause: asking to install two incompatible packages, bestie. The math isn't mathing. 🧮💀
  • 30 — Error in package definition, or other metadata files. Heads up: using --strict raises this error more often. So if you turn on strict mode and see 30, that's on purpose, not a glitch. 🙈
  • 31 — Package script error. Some package operations were unsuccessful. Could be an error in the packages, or an incompatibility with your system. Lowkey this one can be a partial error — like, some of it worked. 😭
  • 40 — Sync error. Could not fetch some remotes from the network. Also potentially a partial error, so check what actually made it through. 📡
  • 50 — Configuration error. Opam or system configuration doesn't allow the operation, and it needs fixing. Girl, you gotta fix the config. 🛠️
  • 60 — Solver failure. The solver failed to return a sound answer. Either a broken external solver, or an error in the solver configuration. The solver is not ok and honestly neither are we. 🤯
  • 99 — Internal error. Something went wrong, and it's likely due to a bug in opam itself. Not your fault for once, bestie. 🐛
  • 130 — User interrupt. SIGINT was received, generally because the user pressed Ctrl+C. You did this. We saw you. 👀

And then there's this extra lil set of codes, coming in hot:

  • 0 — on success.
  • 123 — on indiscriminate errors reported on standard error.
  • 124 — on command line parsing errors.
  • 125 — on unexpected internal errors (bugs).

📚 FURTHER DOCUMENTATION 📚

Need more? The docs live at https://opam.ocaml.org/doc. Go read them, they're giving study session energy. 📖✨

👑 AUTHORS 👑

The icons who built this. Show respect, bestie 💖:

  • David Allsopp <david@tarides.com>
  • Vincent Bernardoff <vb@luminar.eu.org>
  • Raja Boujbel <raja.boujbel@ocamlpro.com>
  • Kate Deplaix <kit-ty-kate@exn.st>
  • 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>

🌸 SEE ALSO 🌸

🐛 BUGS 🐛

Found a bug? Not you being the main character and finding a whole bug 😭 check the bug reports at https://github.com/ocaml/opam/issues and file it there. 🫶

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okay bestie that's the whole page, you ate it, no crumbs 🎀

This was Opam 2.6.1, the page is OPAM-VAR(1), and it's dated like every good manpage is. Now go run something iconic. ✨🦋💅

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📦 where this page comes from