OPAM-WHY(1)

📦
version 2.6.1 · 5 versions
, in arch rolling, fedora 44

💖 opam-why — the opam manual, but make it make sense 💖

OK so bestie, you opened the manual for opam-why(1) and honestly? This one's a little cutie. It's short, it's sweet, and it's lowkey just an alias doing its best. Let's get into it 🫶

✨ NAME ✨

opam-why — literally just an alias for tree --rev-deps. That's the whole personality. It's giving "new phone who dis" except the phone is opam tree in a trench coat 💅

🌸 SYNOPSIS 🌸

opam why [--recursive] [--subpath=PATH] [OPTION]… [PACKAGES]…

Like, you pass it some packages, it tells you why they matter to the dependency graph. Iconic behavior, no notes 🎀

🦋 DESCRIPTION 🦋

So here's the tea: opam why is an alias for opam tree --rev-deps. Same command, different name, zero drama 💖

If you want the actual full details, go read opam tree --help. This page is just the vibe check.

🌈 TREE FILTERING OPTIONS 🌈

These ones decide which slice of the tree you actually get to see. Very "choose your own adventure" of it ✨

  • --leads-to — Shows you only the branches that lead to one of the PACKAGES. So if you're like "okay but WHY does this package exist in my life", this is the one 🕵️💖
  • --roots-from — Shows only the trees that root from one of the PACKAGES. And yes, this is the default, so if you didn't ask for anything else, this is what you're getting, no cap 👑

🌟 TREE BUILDING OPTIONS 🌟

Now we're building the actual forest. Unhinged that a CLI has a forest but okay, we love a nature metaphor 🌳

  • --deps — Draws a dependency forest, starting from the packages that nothing else requires. Basically the top-level girlies. And this is the default 💅
  • --rev-deps — Draws a reverse-dependency forest, starting from the packages which have no dependencies. The ones holding up nobody but themselves. Main character energy fr fr 🔥

🎀 PACKAGE SELECTION OPTIONS 🎀

Which packages get invited to the party 🎉

  • --dev — Includes development packages in dependencies. Bring them along, they're fun 🫶
  • --no-switch — Ignores the active switch and pretends you're installing packages into a completely empty switch, just to draw the forest. Fresh start, blank slate, no baggage ✨
  • --post — Includes dependencies tagged as post. Not pre, not mid — post 🙈
  • -t, --with-test, --test — Includes test-only dependencies. Three names, one icon 💕
  • --with-dev-setup — Includes developer-only dependencies. You know, the ones only you need, bestie 🧚
  • --with-doc, --doc — Includes doc-only dependencies. For the readers, the learners, the girlies who read the docs 📚🌸

⭐ OUTPUT FORMAT OPTIONS ⭐

  • --no-constraint — Hides the version constraints, like (>= 1.0.0). So you get the vibes without the numbers 💫

💜 ARGUMENTS 💜

  • PACKAGES — A list of package names, and you can toss in an optional version or constraint, like pkg, pkg.1.0 or pkg>=0.5. OR you can hand it files or directory names that contain package descriptions — but you must be explicit about the directory, like ./foo.opam or . 🍓 No sneaky implicit paths, the command will not be doing that guesswork for you.

🔥 OPTIONS 🔥

  • --recursive — Allows recursive lookups of *.opam files. Also peep --subpath, they're besties 💞
  • --subpath=PATH — Grabs the *.opam files from the given subdirectory instead of the top directory. Sources get taken from that targeted subdirectory too — internally, only that subdirectory is copied/fetched. You can pair it with --recursive to do a recursive lookup on the subpath. Combo move 🤝

👑 COMMON OPTIONS 👑

These are the options that show up across all the commands. The shared wardrobe, if you will 💅

  • --best-effort — Won't fail just because not every requested package can be installed: it'll try to install as many as it can. Heads up though, not all external solvers support this (recent versions of aspcud or mccs should). It's 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 meant 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 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. iykyk 🌈
  • --color=WHEN — Colorizes the output. WHEN must be one of always, never or auto. We love a little sparkle ✨
  • --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. Multiple times! It's giving layers 💀
  • --criteria=CRITERIA — Specify 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. Homework assigned, bestie 📖
  • --cudf=FILENAME — Debug option: saves 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. Deep lore 🔍
  • --debug — Prints debug messages to stderr. Equivalent to setting $OPAMDEBUG to "true".
  • --debug-level=LEVEL — Like --debug, but you get to specify the debug level (--debug sets it to 1). Equivalent to setting $OPAMDEBUG to a positive integer. Turn that dial up 🎚️
  • --git-version — Prints the git version of opam, if it's set (i.e. you're on a development version), and exits. Peek behind the curtain 🎭
  • --help[=FMT] (default=auto) — Shows this help in format FMT. 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. You are here 📍
  • --ignore-pin-depends — Ignores extra pins required by packages that get pinned, whether that's manually through opam pin or through opam install DIR. Equivalent to setting IGNOREPINDEPENDS=true.
  • --json=FILENAME — Saves the results of the opam run into a computer-readable file. If the filename contains the character %, it gets replaced by an index that doesn't overwrite an existing file. Similar to setting the $OPAMJSON variable. Machine-readable slay 🤖
  • --no — Answers no to all opam yes/no questions without prompting. See also --confirm-level. Equivalent to setting $OPAMNO to "true". Respectfully declining everything 🙅♀️
  • --no-aspcud — Removed in 2.1. She's gone, she's retired, we don't talk about her 💀
  • --no-auto-upgrade — When configuring or updating a repository that was written for an earlier opam version (1.2), opam internally converts it to the current format. This disables that behavior. Note that repositories should define their format version in a 'repo' file at their root, otherwise they'll 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 behavior. No auto-glow-up for opam today 🚫
  • -q, --quiet — Disables --verbose. Shhh 🤫
  • --root=ROOT — Uses ROOT as the current root path. Equivalent to setting $OPAMROOT to ROOT.
  • --safe, --readonly — Makes sure nothing gets automatically updated or rewritten. Handy for calling from completion scripts, for example. It will fail whenever such an operation is needed; it also avoids waiting for locks, skips interactive questions and overrides the $OPAMDEBUG variable. Equivalent to setting the environment variable $OPAMSAFE. Look but don't touch 🫶
  • --solver=CMD — Specifies 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}%. Equivalent to setting $OPAMEXTERNALSOLVER. Pick your fighter ⚔️
  • --strict — Fails whenever an error is found in a package definition or a configuration file. The default is to continue silently if possible. Zero tolerance mode 👀
  • --switch=SWITCH — Uses SWITCH as the current compiler switch. Equivalent to setting $OPAMSWITCH to SWITCH.
  • --use-internal-solver — Disables any external solver and uses the built-in one (this requires that opam was compiled with a built-in solver). Equivalent to setting $OPAMNOASPCUD or $OPAMUSEINTERNALSOLVER. Homegrown, organic, locally-sourced solving 🌱
  • -v, --verbose — Be more verbose. One -v shows all package commands; repeat it to also display commands called internally (e.g. tar, curl, patch etc.). Repeating n times is equivalent to setting $OPAMVERBOSE to "n". Tell me everything 🗣️
  • --version — Shows 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're pointing to. Careful though: since the source directory is copied as it is, if it isn't clean it may result in an opam build failure 💀 This only affects packages explicitly listed on the command-line. It can also be set with $OPAMWORKINGDIR.
  • -y, --yes — Answers yes to all opam yes/no questions without prompting. See also --confirm-level. Equivalent to setting $OPAMYES to "true". Yes bestie, obviously 💖
ok that's the first chunk! more of this manual is coming, so don't go anywhere 🌸

✨ ENVIRONMENT ✨

okay so bestie, opam is lowkey obsessed with environment variables 💖 it reads a whole bunch of them, and here's the entire list, no skips, no shortcuts, we're doing all of them.

First the rules of the game for the boolean ones: set them to "0", "no", "false" or the empty string to disable them, and "1", "yes" or "true" to enable them. That's it, that's the vibe check 🌸

  • OPAMALLPARENS — surrounds all filters with parenthesis 🎀
  • OPAMASSUMEDEPEXTS — see option --assume-depexts.
  • OPAMAUTOANSWER — internal use only 🙈
  • 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. gone, girl, gone 💀
  • OPAMBUILDTEST — Removed in 2.1. also gone.
  • 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. parallel downloads? slay 🔥
  • 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. it really said "i'm the main character here" 👑
  • 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 and reinstall.
  • OPAMIGNOREAVAILABLE — see install option --ignore-available-on.
  • 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.
  • OPAMNOASPCUD — Deprecated. 👵 she's retired, leave her be.
  • 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. keep trying bestie, we believe in you 🫶
  • 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.
⚠️ okay babe, that one is Unsafe. it's for compatibility testing only. don't be out here living dangerously for no reason 💀
  • 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. bye bestie 🦋
  • 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 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. 🐪🐪 camels!! iconic.
  • 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. 🚫 literally just don't, i'm telling you as a friend.
  • OPAMWITHDEVSETUP — see install option --with-dev-setup.
  • 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 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 listen up because this one is a vibe and also genuinely important 🎀

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.

💅 the way that "environment variable controlling the parsing of syntax is brittle" is such a read. they're basically saying: please use the flag, bestie, the env var is giving fragile energy. and yes, last --cli wins, so don't stack them expecting the first one to matter, she's overruled 👑

💀 EXIT STATUS 💀

okay so before we get into the numbers, hear me out, there's ONE exception and she's first: the exec command is built different. She returns 127 if the command was not found or couldn't be executed, and otherwise she returns the command's own exit value. everyone else? they follow the list. periodt.

  • 0 — Success bestie!! 🎉 Or true for boolean queries. slay.
  • 1 — False. She shows up when a boolean return value is expected, like when you're running with --check, or for queries like opam lint. it's giving "no 💅" and that's valid.
  • 2 — Bad command-line arguments, OR command-line arguments pointing to an invalid context (e.g. a file that doesn't follow the expected format). literally the args said nonsense 🙈
  • 5 — Not found. You requested something (package, version, repository, etc.) and it couldn't be found. ghosted fr fr 👻
  • 10 — Aborted. The operation required confirmation, and the confirmation wasn't given. no consent no operation, we love boundaries 💖
  • 15 — Could not acquire the locks required for the operation. the door was locked babe 🔒
  • 20 — There is no solution to the user request. This can be caused by asking to install two incompatible packages, for example. they're not compatible, it's not gonna work, stop trying to make fetch happen 😭
  • 30 — Error in package definition, or other metadata files. Heads up: using --strict raises this error more often. ✨stricter✨ means more of this.
  • 31 — Package script error. Some package operations were unsuccessful. This may be an error in the packages or an incompatibility with your system. Also, this can be a partial error. so like, some of it worked, some of it didn't 🫠
  • 40 — Sync error. Could not fetch some remotes from the network. And yep, this can also be a partial error. the wifi said not today 🌧️
  • 50 — Configuration error. Opam or system configuration doesn't allow the operation, and it needs fixing. config said no 💅
  • 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. the math girlie is not mathing 🧮💀
  • 99 — Internal error. Something went wrong, and it's likely due to a bug in opam itself. not your fault bestie, she's just having a moment 😭
  • 130 — User interrupt. SIGINT was received, generally because the user pressed Ctrl+C. that was you. you did that. 🙈

and then there's this second little squad, which is the general convention situation, lowkey:

  • 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 📚

the lore is deep and she's online: see https://opam.ocaml.org/doc. go read, it's giving academic baddie ✨

👑 AUTHORS 👑

the icons the legends the literal main characters who built this. show some respect, say thank you 💖

  • 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 🔗

  • opam(1) — yeah go read the main one, she's the blueprint 🎀

🐛 BUGS 🐛

found something cursed? Check bug reports at https://github.com/ocaml/opam/issues. do NOT suffer in silence, that's not the vibe, the girls are on GitHub handling it 🫶

and that's the whole page bestie!! 💅 no cap, you now know opam why better than most people know their own passwords. this was OPAM-WHY(1) from the Opam 2.6.1 era, so if you're reading this in the future and something's different, that's a future-you problem, not mine 🌸 go forth, be the main character of your own switch, and remember: your packages can't explain themselves unless you ask nicely. obsessed with you. bye!! ✨🦋💖

📦 where this page comes from