OPAM

https://opam.ocaml.org/doc/
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OPAM is a package manager for OCaml that handles installation, dependency management, and version...
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### OPAM Install Preferences Example

Source: https://opam.ocaml.org/doc/1.2/Specifying_Solver_Preferences

Demonstrates how to set default preferences for installing packages in OPAM. This aims to minimize changes to the existing system.

```shell
export OPAMCRITERIA="-removed,-changed,-notuptodate"
```

--------------------------------

### Opam: Include Development Setup Dependencies

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

The `--with-dev-setup` option includes dependencies required for development tools.

```bash
--with-dev-setup
```

--------------------------------

### OPAM Install File: Manually Installing Binary Files

Source: https://opam.ocaml.org/doc/1.1/Packaging

This '.install' file example shows how to manually specify the installation of a binary file, mapping a source path to a destination name within the OPAM environment.

```ocaml
bin: ["_build/test/xmltrip.native" {"xmltrip"}]

```

--------------------------------

### Opam: Get Help in Specific Format

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Retrieve help information in a specified format using the --help option. Supported formats include 'auto', 'pager', 'groff', and 'plain'.

```bash
opam --help=plain
```

```bash
opam --help=pager
```

--------------------------------

### Install OPAM Package

Source: https://opam.ocaml.org/doc/1.1/Packaging

Provides an example of how to install a specific version of an OPAM package using the 'opam install' command.

```bash
opam install ounit.1.1.3
```

--------------------------------

### Install Opam using Binary Distribution Script

Source: https://opam.ocaml.org/doc/1.2/Install

This snippet downloads and executes an installation script to install opam. It checks the system architecture and installs a pre-compiled binary, followed by running 'opam init'.

```bash
wget https://raw.github.com/ocaml/opam/master/shell/opam_installer.sh -O - | sh -s /usr/local/bin
```

--------------------------------

### Opam Automatic Pinning and Installation

Source: https://opam.ocaml.org/doc/2.0/Upgrade_guide

Demonstrates how to pin and install packages directly from the current directory, including dependency installation.

```ocaml
opam install .
```

```ocaml
opam install . --deps-only
```

--------------------------------

### Install OPAM using Binary Installer

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Downloads and executes a script to install OPAM. Allows specifying the installation path and OCaml version.

```shell
wget https://raw.github.com/ocaml/opam/master/shell/opam_installer.sh
sh ./opam_installer.sh /usr/local/bin
```

```shell
sh ./opam_installer.sh /usr/local/bin 3.12.1 # Install the latest OPAM and OCaml 3.12.1
```

```shell
sh ./opam_installer.sh /usr/local/bin system # Install the latest OPAM using the system compiler (if any)
```

--------------------------------

### Getting a local copy and installing an OPAM package

Source: https://opam.ocaml.org/doc/1.2/Packaging

This command retrieves a local copy of an existing OPAM package and prepares it for installation from that local source. It's useful for development or testing.

```bash
$ opam source <package> --pin
```

--------------------------------

### Install OPAM

Source: https://opam.ocaml.org/doc/1.1/Advanced_Install

This snippet shows the command to install OPAM after it has been compiled. The installation location depends on the prefix specified during the configure phase.

```bash
sudo make install
```

--------------------------------

### Create Fast Compiler Switch

Source: https://opam.ocaml.org/doc/1.1/FAQ

Example of creating a new OPAM switch using an already installed system compiler, leading to faster switch creation.

```shell
opam switch myswitch --alias-of system
```

--------------------------------

### Opam: Include Development Setup Dependencies

Source: https://opam.ocaml.org/doc/2.0/man/opam-install

The `--with-dev-setup` option includes dependencies required for development tools.

```bash
--with-dev-setup
```

--------------------------------

### Get opam help

Source: https://opam.ocaml.org/doc/2.0/FAQ

This command provides a starting point for understanding opam's functionality and usage through its command-line interface. It displays help information, similar to git's help system.

```shell
opam --help
```

--------------------------------

### Opam: Get Help in Specific Format

Source: https://opam.ocaml.org/doc/2.0/man/opam-install

Retrieve help information in a specified format using the --help option. Supported formats include 'auto', 'pager', 'groff', and 'plain'.

```bash
opam --help=plain
```

```bash
opam --help=pager
```

--------------------------------

### Advanced Solver Criteria Example

Source: https://opam.ocaml.org/doc/2.0/External_solvers

An example of advanced solver preferences using a syntax compatible with `aspcud >=1.8.0`. This criteria string aims to minimize downgrades, installed size, and the number of changed packages, among other factors.

```plaintext
-count(removed),-count(down),-sum(solution,installedsize),-notuptodate(solution),-count(changed)
```

--------------------------------

### Opam Install to Destdir

Source: https://opam.ocaml.org/doc/2.0/Upgrade_guide

Explains how to copy build artifacts of packages to an external directory prefix.

```ocaml
opam install --destdir
```

--------------------------------

### List Installed OPAM Switches

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Lists all currently installed OPAM switches. This command provides an overview of the available environments.

```bash
opam switch list
```

--------------------------------

### Compile OPAM from Source

Source: https://opam.ocaml.org/doc/1.1/Advanced_Install

This snippet shows how to compile OPAM from its source code. It includes the basic compilation steps and how to specify a custom installation prefix.

```bash
./configure
make
```

```bash
./configure --prefix=/the/opam/path
make
```

--------------------------------

### Install opam-devel

Source: https://opam.ocaml.org/doc/2.0/FAQ

This snippet demonstrates how to install the development version of opam, which is useful for upgrading an existing opam installation. It involves using opam itself to bootstrap the new version.

```shell
opam install opam-devel
```

--------------------------------

### Install opam manually

Source: https://opam.ocaml.org/doc/2.0/Install

This command demonstrates how to manually install a downloaded opam binary to the system's PATH, making it executable. This method is an alternative if the script-based installation encounters issues.

```bash
sudo install <downloaded file> /usr/local/bin/opam
```

--------------------------------

### Install opam on FreeBSD

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam using the pkg install command on FreeBSD.

```bash
pkg install ocaml-opam
```

--------------------------------

### Opam Installer File Handling

Source: https://opam.ocaml.org/doc/2.0/api/index

Handles the processing of Opam's `.install` files, which define how packages are installed and configured.

```OCaml
opam_installer.ml | Handles opam's ".install" files
```

--------------------------------

### Get Information About an OPAM Package

Source: https://opam.ocaml.org/doc/1.1/Advanced_Usage

Displays detailed information about a specific OPAM package, including its installed version, all available versions, and a full description. This is useful for understanding package contents and compatibility.

```shell
opam info opam
```

--------------------------------

### Install OPAM on Guix

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Installs the OPAM package on Guix and Guix System using the guix install command.

```shell
guix install opam
```

--------------------------------

### Install opam on OpenBSD

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam using the pkg_add command on OpenBSD.

```bash
pkg_add opam
```

--------------------------------

### Install and Remove Packages with opam

Source: https://opam.ocaml.org/doc/2.0/Usage

Installs a specified package and its dependencies, or uninstalls a package. The install command handles downloading, building, and installing.

```shell
# ** Install **
opam install PACKAGE # Download, build and install the latest version of PACKAGE
                     # and all its dependencies
opam remove PACKAGE  # Uninstall the given package

```

--------------------------------

### Install Packages with OPAM and Resolve Conflicts

Source: https://opam.ocaml.org/doc/1.2/FAQ

Demonstrates how to install packages with OPAM and provides strategies for resolving conflicts or forcing specific package versions. It highlights the use of `opam install` with package names and version constraints.

```Shell
opam install foo bar
```

```Shell
opam install foo.2.0 bar.1.1
```

```Shell
opam install 'foo>=2.0'
```

--------------------------------

### Opam: Include developer setup dependencies

Source: https://opam.ocaml.org/doc/2.0/man/opam-list

The --with-dev-setup option includes dependencies specifically required for developer setup, ensuring a complete development environment.

```bash
--with-dev-setup
```

--------------------------------

### Manually Install Opam Binary

Source: https://opam.ocaml.org/doc/1.2/Install

This method involves downloading a pre-compiled opam binary and manually copying it to a directory in the system's PATH.

```bash
sudo cp <downloaded file> /usr/local/bin
```

--------------------------------

### Opam Install Commands

Source: https://opam.ocaml.org/doc/1.2/Manual

Demonstrates how to define installation commands in an opam file. Similar to build commands, these are executed after the build phase to move files and configure the installation.

```Opam
install: [
  [ "make" "install" ]
]
```

--------------------------------

### Opam Build and Install Instructions with Filters

Source: https://opam.ocaml.org/doc/2.0/Manual

Specifies instructions for building and installing packages, allowing filters based on variables like 'with-test' and 'with-doc'. Deprecated 'build-test' and 'build-doc' fields are mentioned, with a recommendation to use 'build:' and 'install:' with appropriate filters.

```Opam
build: [ [ <term> { <filter> } ... ] { <filter> } ... ]
install: [ [ <term> { <filter> } ... ] { <filter> } ... ]
```

--------------------------------

### Install opam using Bash script

Source: https://opam.ocaml.org/doc/2.0/Install

This script downloads and installs the latest pre-compiled opam binary for your system. It handles architecture checks, backups of older versions, and runs `opam init`. It's recommended for end-users.

```bash
bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh)"
```

--------------------------------

### Build and Install ounit Package

Source: https://opam.ocaml.org/doc/1.1/Packaging

Demonstrates the basic build and installation commands for the 'ounit' OPAM package using 'make'. These commands are typical for many OCaml projects packaged with OPAM.

```Shell
make build
make install
```

--------------------------------

### Initialize OPAM Environment

Source: https://opam.ocaml.org/doc/1.1/Advanced_Install

This snippet covers the initialization of OPAM's state and environment. It creates configuration files, adds a default repository, and sets up the environment variables for using OPAM.

```bash
opam init
eval `opam config env`
```

--------------------------------

### OPAM Install File: Manually Installing Library Files

Source: https://opam.ocaml.org/doc/1.1/Packaging

This '.install' file snippet demonstrates how to manually install library files, specifying multiple files to be placed in the OPAM 'lib' directory.

```ocaml
lib: [ "META" "lib/foo.cmi" "lib/foo.cmo" "lib/foo.cmx" ]

```

--------------------------------

### Install opam on Mageia

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam using the urpmi package manager on Mageia.

```bash
urpmi opam
```

--------------------------------

### Add and Install Local OPAM Package Repository

Source: https://opam.ocaml.org/doc/1.1/FAQ

This shows how to set up a local OPAM repository for developing and installing custom packages. It involves creating a directory structure, adding it as a remote, updating OPAM's package index, and then installing the new package.

```bash
mkdir -p my-repo/packages
opam remote add localdev my-repo
opam update
opam install <new-package>
```

--------------------------------

### Install OPAM on Mageia

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Installs the OPAM package on Mageia using the urpmi command.

```shell
urpmi opam
```

--------------------------------

### Install Opam and OCaml on Ubuntu using PPA

Source: https://opam.ocaml.org/doc/1.2/Install

Installs opam, OCaml, and related packages on Ubuntu by adding a Personal Package Archive (PPA). This method is recommended for 'Precise' and 'Trusty' Ubuntu versions.

```bash
add-apt-repository ppa:avsm/ppa
apt-get update
apt-get install ocaml ocaml-native-compilers camlp4-extra opam
```

--------------------------------

### Opam Install File Fields

Source: https://opam.ocaml.org/doc/2.0/Manual

Specifies the installation instructions for Opam packages using the '<pkgname>.install' file. It lists files to be installed into various directories like 'bin', 'lib', 'etc', and 'share', with options for destination paths and executable bits.

```opam
lib: [ "<filename>" { "<destination_filename>" } ]
lib_root: [ "<filename>" { "<destination_filename>" } ]
libexec: [ "<filename>" { "<destination_filename>" } ]
libexec_root: [ "<filename>" { "<destination_filename>" } ]
bin: [ "<filename>" { "<destination_filename>" } ]
sbin: [ "<filename>" { "<destination_filename>" } ]
toplevel: [ "<filename>" { "<destination_filename>" } ]
share: [ "<filename>" { "<destination_filename>" } ]
share_root: [ "<filename>" { "<destination_filename>" } ]
etc: [ "<filename>" { "<destination_filename>" } ]
doc: [ "<filename>" { "<destination_filename>" } ]
stublibs: [ "<filename>" { "<destination_filename>" } ]
man: [ "<filename>" { "<destination_filename>" } ]
misc: [ "<filename>" { "<destination_filename>" } ]
```

--------------------------------

### Install Opam with ocamlbrew

Source: https://opam.ocaml.org/doc/1.2/Install

This command downloads and executes the ocamlbrew-install script to bootstrap an OCaml environment including Opam. It uses curl to fetch the script and pipes it to bash, with OCAMLBREW_FLAGS set to '-r' for a remote installation.

```bash
curl -kL https://raw.github.com/hcarty/ocamlbrew/master/ocamlbrew-install | env OCAMLBREW_FLAGS="-r" bash
```

--------------------------------

### Update Package Database and Install Packages with OPAM

Source: https://opam.ocaml.org/doc/1.1/Basic_Usage

These are fundamental commands for managing packages with OPAM. 'opam update' refreshes the local package database, and 'opam install PACKAGE' downloads, builds, and installs a specified package.

```bash
opam update             # Update the packages database
opam install PACKAGE    # Download, build and install the latest version of PACKAGE
```

--------------------------------

### Opam: Link Libraries with OCamlfind

Source: https://opam.ocaml.org/doc/2.0/FAQ

Explains how to link libraries installed with opam using `ocamlfind`. It details the default installation directory and how to use `ocamlfind query`.

```bash
ocamlfind query <lib>
```

--------------------------------

### Share OCaml Switch Setup with opam lock

Source: https://opam.ocaml.org/doc/2.0/FAQ

Generates a locked opam file containing exact dependency versions for a specific package, allowing for easy sharing of a working switch setup. This file can be checked into version control or shared directly. The `opam install --locked` command can then be used to install packages based on this locked file.

```bash
$ opam lock <pkg> # generate a <pkg>.opam.lock file
$ opam install --locked <pkg> # use <pkg> locked file, if present
```

--------------------------------

### Install and Manage OPAM Packages

Source: https://opam.ocaml.org/doc/1.2/Packaging

Commands for installing, pinning, and removing OPAM packages. It also includes editing the opam file for package metadata.

```bash
$ opam install <project> --verbose
$ opam remove <project>
$ opam pin edit <project>
```

--------------------------------

### Install OPAM on Ubuntu

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Installs OCaml and OPAM on Ubuntu by adding a PPA and updating the package list. Requires 'python-software-properties' if 'add-apt-repository' is not available.

```shell
add-apt-repository ppa:avsm/ppa
apt-get update
apt-get install ocaml opam
```

--------------------------------

### Advanced opam Preferences with aspcud Solver

Source: https://opam.ocaml.org/doc/1.2/Specifying_Solver_Preferences

This example illustrates advanced user preferences for the opam package manager using the aspcud solver (version 1.8.0 or later). It demonstrates minimizing downgrades and installed size using criteria like `-count(removed), -count(down), -sum(solution,installedsize), -notuptodate(solution), -count(changed)`.

```bash
-count(removed), -count(down),-sum(solution,installedsize),-notuptodate(solution),-count(changed)
```

--------------------------------

### List OPAM Repositories

Source: https://opam.ocaml.org/doc/1.1/Packaging

Shows how to list all configured OPAM repositories using the 'opam repo' command.

```bash
opam repo
```

--------------------------------

### Basic Opam Build and Install Commands

Source: https://opam.ocaml.org/doc/2.0/Packaging

Defines how to compile and install a package using opam. It supports using variables like 'make' and environment prefixes like '%{prefix}%'. The 'install' field can be omitted if a package generates an '.install' file, common with Dune.

```ocaml
build: [ ["./configure"]] 
install: [ [make "install"] ]
```

--------------------------------

### Install Opam on Debian using APT

Source: https://opam.ocaml.org/doc/1.2/Install

Installs opam on Debian-based systems using the apt-get package manager. This command fetches opam from the official repositories.

```bash
apt-get install opam
```

--------------------------------

### Install Specific Package Versions and Constraints

Source: https://opam.ocaml.org/doc/1.2/Usage

Demonstrates how to install specific packages, including version constraints. This allows for precise control over the versions of libraries and tools installed in the OPAM environment.

```ocaml
opam install lwt
opam install ocp-indent ocp-index.1.0.2
opam install "ocamlfind>=1.4.0"
```

--------------------------------

### Build OPAM from Sources

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Compiles and installs OPAM from its source code. Requires downloading the source archive first.

```shell
./configure && make && make install
```

--------------------------------

### Install OPAM using ocamlbrew

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Bootstraps an OCaml environment including OPAM from source using the ocamlbrew script. Does not require an existing OCaml installation.

```shell
curl -kL https://raw.github.com/hcarty/ocamlbrew/master/ocamlbrew-install | env OCAMLBREW_FLAGS="-r" bash
```

--------------------------------

### Install Opam on OpenBSD using Ports

Source: https://opam.ocaml.org/doc/1.2/Install

Installs opam on OpenBSD version 5.7 or higher by building it from the ports tree.

```bash
cd /usr/ports/sysutils/opam
make install
```

--------------------------------

### List Available Compiler Packages

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Lists all packages recommended for installation when creating a new switch, specifically those flagged with the `compiler` attribute. It can optionally show all versions or include packages marked as `avoid-version` or `deprecated`.

```bash
opam switch list-available [PATTERN] [--all]
```

--------------------------------

### Install opam using PowerShell script on Windows

Source: https://opam.ocaml.org/doc/2.0/Install

This PowerShell script installs the latest pre-compiled opam binary on Windows. It performs similar actions to the bash script, including downloading, backing up, and initializing opam.

```powershell
Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) }"
```

--------------------------------

### List, Search, and Get Package Info with OPAM

Source: https://opam.ocaml.org/doc/1.1/Basic_Usage

These commands allow you to discover and retrieve information about available packages in OPAM. 'opam list -a' lists all packages, 'opam search QUERY' finds packages matching a query, and 'opam info PACKAGE' displays details about a specific package.

```bash
opam list -a            # List all available packages
opam search QUERY       # List packages with QUERY in their name or description
opam info PACKAGE       # Display information about PACKAGE
```

--------------------------------

### List Installable OPAM Packages

Source: https://opam.ocaml.org/doc/2.0/man/opam-list

Lists only packages that can be installed on the current switch. This may involve calling the solver and can be more computationally intensive.

```shell
opam list --installable
```

--------------------------------

### Opam Misc File Installation

Source: https://opam.ocaml.org/doc/1.2/Manual

Describes the installation of miscellaneous files. This requires specifying an absolute destination for each file, and the user will be prompted before installation.

```opam
misc: [ <string> { <string> } ]
```

--------------------------------

### OPAM: Install Packages

Source: https://opam.ocaml.org/doc/2.0/man/opam

Installs a specified list of OCaml packages using OPAM. This command handles all necessary dependency resolutions and installations.

```shell
opam install [OPTION]... [PACKAGES]...
```

--------------------------------

### Opam Client Library and Configuration

Source: https://opam.ocaml.org/doc/2.0/api/index

The core `opam-client` library, including configuration options for the library, global references, setters, and initialization helpers. It also handles concrete actions on packages like installations and removals.

```OCaml
src/client | _opam-client_ library and exec
```

```OCaml
opamClientConfig.ml | Configuration options for this lib (record, global reference, setter, initialisation), plus helper for global setup
```

```OCaml
opamAction.ml | Handles concrete actions on packages, like installations and removals
```

--------------------------------

### Advanced opam Preferences with aspcud Solver

Source: https://opam.ocaml.org/doc/1.1/Specifying_Solver_Preferences

This example illustrates advanced user preferences for the opam package manager using the aspcud solver (version 1.8.0 or later). It demonstrates minimizing downgrades and installed size using criteria like `-count(removed), -count(down), -sum(solution,installedsize), -notuptodate(solution), -count(changed)`.

```bash
-count(removed), -count(down),-sum(solution,installedsize),-notuptodate(solution),-count(changed)
```

--------------------------------

### Create Local OCaml Switch with Dependencies Only

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Prepares a local OCaml switch for building packages in the current directory. It scans for package definitions, selects a compatible compiler, creates the switch, and installs project dependencies.

```bash
opam switch create ./ --deps-only
```

--------------------------------

### Compile OPAM on BSD Systems

Source: https://opam.ocaml.org/doc/1.1/Advanced_Install

This snippet demonstrates how to compile OPAM on BSD systems, which requires using `gmake` instead of `make` and specifying a different path for manual pages.

```bash
./configure --mandir /usr/local/man
gmake
```

--------------------------------

### Opam Cygwin Setup and SPDX License List

Source: https://opam.ocaml.org/doc/2.0/api/index

Contains generated code for Cygwin setup if specified in the configure process, and a list of SPDX short IDs for licenses used in package linting.

```OCaml
opamEmbedCygwinSetup.ml | (generated) Contains the Cygwin setup.exe binary if specified in the configure
```

```OCaml
opamSpdxList.ml | (generated) SPDX short IDs licenses list, used for linting packages
```

--------------------------------

### Opam Upgrade to Fix Package Set

Source: https://opam.ocaml.org/doc/2.0/External_solvers

Shows how to use the `opam upgrade` command with specific criteria to repair the set of installed packages. This example uses `"-changed"` to minimize changes, which can be useful for system maintenance.

```bash
opam upgrade --criteria="-changed"
```

--------------------------------

### Opam Initialization Defaults and Client Main Entry Point

Source: https://opam.ocaml.org/doc/2.0/api/index

Defines the default `opamrc` used during `opam init` and provides high-level execution wrappers for main user commands like install, upgrade, and remove, including wrappers for Pin commands. It also includes front-end wrappers for the main Opam entry point.

```OCaml
opamInitDefaults.ml | Defines the built-in "opamrc" to use by default on "opam init"
```

```OCaml
opamClient.ml | High-level execution of the main user commands ("install", "upgrade", "remove"), and wrapper for Pin commands
```

```OCaml
opamCliMain.ml | Front-end wrappers and callers for the main opam entry point
```

--------------------------------

### Install Opam Package in All Switches

Source: https://opam.ocaml.org/doc/2.0/Tricks

Provides a shell script to install a specified package across all available Opam switches. It iterates through listed switches and applies the 'opam install' command.

```shell
for switch in $(opam switch list -s); do
  opam install --switch $switch PACKAGE
done
```

--------------------------------

### Prepare and Package Project for OPAM

Source: https://opam.ocaml.org/doc/1.2/Packaging

Steps to prepare a project for the OPAM repository, including using opam-publish to create package files or manually creating 'descr' and 'url' files.

```bash
$ opam install opam-publish
$ opam-publish prepare <URL>
```

```bash
archive: "https://address/of/project.1.0.tar.gz"
checksum: "3ffed1987a040024076c08f4a7af9b21"
```

```bash
$ curl -L "https://address/of/project.1.0.tar.gz" | md5sum
```

--------------------------------

### Opam User Preferences Syntax

Source: https://opam.ocaml.org/doc/2.0/External_solvers

User preferences in Opam are expressed using a simple language with combinators prefixed by '+' or '-'. These preferences guide the dependency solver to minimize or maximize certain criteria during package installation. Combinations are processed lexicographically.

```Shell
# Minimize removed packages
-removed

# Maximize new packages
+new

# Combined preferences (lexicographic order)
-removed,+changed,-notuptodate
```

--------------------------------

### Opam Install with Custom Criteria

Source: https://opam.ocaml.org/doc/2.0/External_solvers

Demonstrates how to specify custom installation criteria using the `--criteria` option in the Opam command line. This allows users to fine-tune the installation process based on specific preferences like minimizing removals or changes.

```bash
opam install --criteria="-removed,-changed" ...
```

--------------------------------

### Create a New OPAM Switch

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Creates a new OPAM switch with a specified compiler. The switch can be a named prefix or a directory for a local switch. If package definitions are found in a local switch's directory, compatible compilers are searched, and packages are installed automatically unless `--no-install` is used.

```bash
opam switch create SWITCH [COMPILER]
```

--------------------------------

### Install and Upgrade OPAM Packages

Source: https://opam.ocaml.org/doc/1.2/Usage

Installs packages and their dependencies, and updates the package database. `opam install` handles downloading and building, while `opam update` and `opam upgrade` manage the overall package versions.

```ocaml
opam install PACKAGE # Download, build and install the latest version of PACKAGE
                     # and all its dependencies
opam update          # Update the packages database
opam upgrade         # Bring everything to the latest version possible
```

--------------------------------

### Install System Dependencies with opam depext

Source: https://opam.ocaml.org/doc/2.0/FAQ

Installs external system libraries required by OCaml packages. The `opam depext` command, when used with package names, will install the `opam-depext` plugin if needed and then prompt to install the necessary system packages using the OS's package manager. This is useful when compilation fails due to missing non-OCaml dependencies.

```bash
opam depext <opam-packages>
```

--------------------------------

### Install External Dependencies with OPAM

Source: https://opam.ocaml.org/doc/1.2/FAQ

This snippet shows how to install system-level dependencies required by OCaml packages using the `opam-depext` tool. It first installs the tool itself and then uses it to fetch dependencies for specified packages.

```Shell
opam install depext
opam depext <packages>
```

--------------------------------

### Install opam on Guix & Guix System

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam using the guix install command on Guix and Guix System.

```bash
guix install opam
```

--------------------------------

### Opam Core Commands Index

Source: https://opam.ocaml.org/doc/2.0/man/index

This snippet lists core Opam commands for managing packages and the environment. It includes commands for cleaning, configuring, setting environment variables, executing commands, displaying help, retrieving information, initializing, installing, linting, listing, locking, setting options, pinning, reinstalling, managing remotes, removing, handling repositories, searching, showing details, sourcing, managing switches, and displaying trees.

```text
opam-clean.0
opam-clean
opam-clean.err
opam-config.0
opam-config
opam-config.err
opam-env.0
opam-env
opam-env.err
opam-exec.0
opam-exec
opam-exec.err
opam-help.0
opam-help
opam-help.err
opam-info.0
opam-info
opam-info.err
opam-init.0
opam-init
opam-init.err
opam-install.0
opam-install
opam-install.err
opam-installer
opam-lint.0
opam-lint
opam-lint.err
opam-list.0
opam-list
opam-list.err
opam-lock.0
opam-lock
opam-lock.err
opam-option.0
opam-option
opam-option.err
opam-pin.0
opam-pin
opam-pin.err
opam-reinstall.0
opam-reinstall
opam-reinstall.err
opam-remote.0
opam-remote
opam-remote.err
opam-remove.0
opam-remove
opam-remove.err
opam-repository.0
opam-repository
opam-repository.err
opam-search.0
opam-search
opam-search.err
opam-show.0
opam-show
opam-show.err
opam-source.0
opam-source
opam-source.err
opam-switch.0
opam-switch
opam-switch.err
opam-tree.0
opam-tree
opam-tree.err
opam-uninstall.0
opam-uninstall
opam-uninstall.err
opam-unpin.0
opam-unpin
opam-unpin.err
opam-update.0
opam-update
opam-update.err
opam-upgrade.0
opam-upgrade
opam-upgrade.err
opam-var.0
opam-var
opam-var.err
opam-why.0
opam-why
opam-why.err
opam
```

--------------------------------

### Install Maximum Packages with Opam

Source: https://opam.ocaml.org/doc/2.0/Tricks

This sequence of commands demonstrates how to install the maximum number of available packages into a local Opam switch. It involves updating Opam, creating a new switch, setting solver timeout and tolerance, and then using 'opam list --available -s' piped to 'opam install --best-effort --yes' to install packages.

```bash
opam update
opam switch create . ocaml-base-compiler.$(VERSION)
export OPAMSOLVERTIMEOUT=3600
export OPAMSOLVERTOLERANCE=1.0
opam list --available -s | xargs opam install --best-effort --yes
```

--------------------------------

### Install software-properties-common on Debian/Ubuntu

Source: https://opam.ocaml.org/doc/1.2/Install

Installs the 'software-properties-common' package, which provides the 'add-apt-repository' command, on Debian or Ubuntu systems if it's not already installed.

```bash
apt-get install software-properties-common
```

--------------------------------

### OPAM Install: Local Package Build Options

Source: https://opam.ocaml.org/doc/2.0/man/opam-install

For locally-pinned packages, `opam install` offers options to control the build and installation process. This includes assuming a package is already built or installing directly from its source directory.

```bash
opam install --assume-built package_name
opam install --inplace-build package_name
```

--------------------------------

### Create OCaml Switch with Custom Repository and Compiler

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Creates a new OCaml switch with a specified name, a custom compiler variant, and includes an additional 'beta' repository alongside the default one.

```bash
opam switch create trunk --repos default,beta=https://github.com/ocaml/ocaml-beta-repository.git ocaml-variants.4.10.0+trunk
```

--------------------------------

### Control OPAM Package Installation and Upgrades

Source: https://opam.ocaml.org/doc/1.2/FAQ

Explains how to be more explicit when installing or upgrading OCaml packages with OPAM, such as specifying versions or package names. It also mentions the importance of having an external solver installed for complex package set resolutions.

```Shell
opam upgrade PACKAGES
opam install 'PACKAGE>=VERSION' PACKAGE...
```

--------------------------------

### Opam: Show Actions

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

The `--show-actions` option calls the solver and displays the planned actions without executing any changes. This is equivalent to setting OPAMSHOW.

```bash
--show-actions
```

--------------------------------

### Opam Ignore Constraints

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Allows ignoring specific constraints during installation. This can be useful for bypassing certain dependency requirements when necessary.

```shell
_OPAMIGNORECONSTRAINTS_ see install option ‘--ignore-constraints-on'.
```

--------------------------------

### Export OPAM Switch State

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Saves the current OPAM switch state to a file. The `--full` option includes metadata for all installed packages, and `--freeze` locks all VCS repositories to their current commits.

```bash
opam switch export FILE [--full] [--freeze]
```

--------------------------------

### Install opam on Fedora

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam using the dnf package manager on Fedora.

```bash
dnf install opam
```

--------------------------------

### List All Opam Repositories

Source: https://opam.ocaml.org/doc/2.0/Manual

Provides an overview of all configured opam repositories.

```bash
opam repository list --all
```

--------------------------------

### OPAM Install: Dependency Management Options

Source: https://opam.ocaml.org/doc/2.0/man/opam-install

This command provides options to manage package dependencies during installation. It can install only dependencies, fetch sources without building, or resolve system dependencies.

```bash
opam install --deps-only package_name
opam install --download-only package_name
opam install --depext-only package_name
```

--------------------------------

### Install opam on macOS using MacPort

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam on macOS using the MacPort package manager.

```bash
# MacPort
port install opam
```

--------------------------------

### Opam Fetch Command Configuration

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

Configures how Opam downloads files using custom commands. It allows specifying a command (like wget or curl) and provides placeholders for URL, output file, retries, compression, and checksums.

```shell
_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.
```

--------------------------------

### Install opam on macOS using Homebrew

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam on macOS using the Homebrew package manager.

```bash
# Homebrew
brew install opam
```

--------------------------------

### Install opam on Alpine Linux

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam using the apk package manager on Alpine Linux.

```bash
apk add opam
```

--------------------------------

### Install opam on Arch Linux

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam using the pacman package manager on Arch Linux.

```bash
pacman -S opam
```

--------------------------------

### Install OPAM on Ubuntu Trusty LTS

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Installs OCaml and OPAM on Ubuntu Trusty LTS from the 'universe' repository.

```shell
apt-get update
apt-get install ocaml ocaml-native-compilers camlp4-extra opam
```

--------------------------------

### Install OPAM on Exherbo

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Installs the dev-ocaml/opam package on Exherbo. It may require adding the '::ocaml-unofficial' repository first.

```shell
cave resolve -x dev-opam/ocaml
```

```shell
cave resolve -x repository/ocaml-unofficial
```

--------------------------------

### Opam: Best Effort Installation

Source: https://opam.ocaml.org/doc/2.0/man/opam-install

The --best-effort flag prevents Opam from failing if not all requested packages can be installed, attempting to install as many as possible. This behavior is equivalent to setting the OPAMBESTEFFORT environment variable.

```bash
opam install --best-effort <package_name>
```

--------------------------------

### Install Opam on OSX using MacPorts

Source: https://opam.ocaml.org/doc/1.2/Install

Installs opam on OSX using the MacPorts package manager.

```bash
port install opam                   # MacPort
```

--------------------------------

### Install Opam on Mageia

Source: https://opam.ocaml.org/doc/1.2/Install

Installs the opam package on Mageia Linux using the urpmi package manager.

```bash
urpmi opam
```

--------------------------------

### Install opam on Debian and Ubuntu

Source: https://opam.ocaml.org/doc/2.0/Install

Installs opam using the apt package manager on Debian and Ubuntu systems.

```bash
apt install opam
```

--------------------------------

### Link Libraries with ocamlfind

Source: https://opam.ocaml.org/doc/1.2/FAQ

Explains how to link libraries installed by OPAM using the `ocamlfind` tool. It shows how to query library locations and mentions the importance of adding dependencies when packaging projects.

```Shell
ocamlfind query <lib>
```

--------------------------------

### Install OPAM on OSX

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Installs OPAM on macOS using Homebrew or MacPorts. Includes options for different Homebrew versions.

```shell
brew install opam                   # using Homebrew on OSX Mavericks
```

```shell
brew install opam --without-aspcud  # using Homebrew on OSX Mountain Lion (or lower)
```

```shell
port install opam                   # using MacPort
```

--------------------------------

### Install OPAM on Archlinux

Source: https://opam.ocaml.org/doc/1.1/Quick_Install

Installs the OPAM package on Archlinux using yaourt. For the development version, replace 'opam' with 'opam-git'.

```shell
yaourt -S opam
```

--------------------------------

### Opam: Best Effort Installation

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

The --best-effort flag prevents Opam from failing if not all requested packages can be installed, attempting to install as many as possible. This behavior is equivalent to setting the OPAMBESTEFFORT environment variable.

```bash
opam install --best-effort <package_name>
```

--------------------------------

### Install OCaml Packages with OPAM

Source: https://opam.ocaml.org/doc/2.0/man/opam-install

The `opam install` command is used to install one or more OCaml packages and their dependencies into the currently selected switch. It can accept package names with optional version constraints or paths to local package definitions.

```bash
opam install package_name
opam install package_name>=1.0
opam install ./path/to/package.opam
opam install .
```

--------------------------------

### List Available OPAM Packages

Source: https://opam.ocaml.org/doc/1.1/Advanced_Usage

Displays a list of all available packages in the configured OPAM repositories. Each line shows the package name, its installed version (if any), and a brief description. Base packages, which are modules often bundled with the OCaml installation, are also indicated.

```shell
opam list
```

--------------------------------

### List Explicitly Installed OPAM Packages

Source: https://opam.ocaml.org/doc/2.0/man/opam-list

Lists only packages that were explicitly installed by the user, excluding those installed automatically as dependencies.

```shell
opam list --roots
```

--------------------------------

### Update and Upgrade Installed Packages with OPAM

Source: https://opam.ocaml.org/doc/1.1/Basic_Usage

Regularly running these commands ensures your packages are up-to-date. 'opam update' synchronizes the package database, while 'opam upgrade' reinstalls packages that have been updated since the last upgrade.

```bash
opam update             # Update the packages database
opam upgrade            # Re-install packages that were updated since last upgrade
```

--------------------------------

### OPAM Install: Advanced Path and Root Management

Source: https://opam.ocaml.org/doc/2.0/man/opam-install

This command supports advanced options for managing package sources via subpaths and recursively searching for opam files. It also allows marking packages as installed roots or automatically installed.

```bash
opam install --subpath=./src package_name
opam install --recursive --subpath=./src package_name
opam install --set-root package_name
opam install --unset-root package_name
```

--------------------------------

### Opam Notice Environment Variable

Source: https://opam.ocaml.org/doc/2.0/man/opam-switch

No description

```shell
_OPAMNOENVNOTICE_ Internal.
```

--------------------------------

### OPAM Install: Destination Directory Option

Source: https://opam.ocaml.org/doc/2.0/man/opam-install

The `--destdir` option allows copying installed package files to a specified directory prefix within the opam switch. This can be useful for staging or custom installations, but caution is advised as it may overwrite files.

```bash
opam install --destdir=/path/to/dest package_name
```
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