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.TH "OPAM-SWITCH" 1 "" "Opam 1.2.2" "Opam Manual"
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.SH NAME
.P
opam\-switch \- Manage multiple installation of compilers.
.SH SYNOPSIS
.P
\fBopam switch\fR [\fIOPTION\fR]... [\fICOMMAND\fR] [\fIARG\fR]...
.SH DESCRIPTION
.P
This command allows one to switch between different compiler versions, installing the compiler if \fBopam switch\fR is used to switch to that compiler for the first time. The different compiler versions are totally independent from each other, meaning that OPAM maintains a separate state (e.g. list of installed packages...) for each.
.P
See the documentation of \fBopam switch list\fR to see the compilers which are available, and how to switch or to install a new one.
.SH COMMANDS
.P
Without argument, defaults to \fBlist\fR.
.TP 4
\fISWITCH\fR
With a \fISWITCH\fR argument, defaults to \fBset\fR \fISWITCH\fR.
.TP 4
\fBinstall\fR \fISWITCH\fR
Install the given compiler. The command fails if the switch is already installed (e.g. it will not transparently switch to the installed compiler switch, as with \fBset\fR).
.TP 4
\fBset\fR \fISWITCH\fR
Set the currently active switch, installing it if needed.
.TP 4
\fBremove\fR \fISWITCH\fR
Remove the given compiler.
.TP 4
\fBexport\fR \fIFILE\fR
Save the current switch state to a file.
.TP 4
\fBimport\fR \fIFILE\fR
Import a saved switch state.
.TP 4
\fBreinstall\fR \fISWITCH\fR
Reinstall the given compiler switch. This will also reinstall all packages.
.TP 4
\fBlist\fR 
List compilers. By default, lists installed and `standard' compilers. Use `\-\-all' to get the list of all installable compilers. The first column displays the switch name (if any), the second one the switch state (C = current, I = installed, \-\- = not installed), the third one the compiler name and the last one the compiler description. To switch to an already installed compiler alias (with state = I), use \fBopam switch <name>\fR. If you want to use a new compiler <comp>, use \fBopam switch <comp>\fR: this will download, compile and create a fresh and independent environment where new packages can be installed. If you want to create a new compiler alias (for instance because you already have this compiler version installed), use \fBopam switch <name> \-\-alias\-of <comp>\fR. In case <name> and <comp> are the same, this is equivalent to \fBopam switch <comp>\fR.
.TP 4
\fBshow\fR 
Show the current compiler.
.SH OPTIONS
.TP 4
\fB\-a\fR, \fB\-\-all\fR
List all the compilers which can be installed on the system.
.TP 4
\fB\-A\fR \fICOMP\fR, \fB\-\-alias\-of\fR=\fICOMP\fR
The name of the compiler description which will be aliased.
.TP 4
\fB\-b\fR, \fB\-\-keep\-build\-dir\fR
Keep the build directory. This is equivalent to setting \fB$OPAMKEEPBUILDDIR\fR to "true".
.TP 4
\fB\-d\fR, \fB\-\-build\-doc\fR
Build the package documentation. This is equivalent to setting \fB$OPAMBUILDDOC\fR to "true".
.TP 4
\fB\-\-dry\-run\fR
Simulate the command, but don't actually perform any changes.
.TP 4
\fB\-e\fR \fITAGS\fR, \fB\-\-external\fR=\fITAGS\fR
Display the external packages associated to the given tags. This is deprecated, use `opam list \-\-external' instead
.TP 4
\fB\-\-fake\fR
This option registers the actions into the OPAM database, without actually performing them. WARNING: This option is dangerous and likely to break your OPAM environment. You probably want `\-\-dry\-run'. You've been warned.
.TP 4
\fB\-i\fR, \fB\-\-installed\fR
List installed compiler switches only.
.TP 4
\fB\-j\fR \fIJOBS\fR, \fB\-\-jobs\fR=\fIJOBS\fR
Set the maximal number of concurrent jobs to use. You can also set it using the \fB$OPAMJOBS\fR environment variable.
.TP 4
\fB\-\-json\fR=\fIFILENAME\fR
Save the result output of an OPAM run in a computer\-readable file
.TP 4
\fB\-m\fR \fIMAKE\fR, \fB\-\-make\fR=\fIMAKE\fR
Use \fIMAKE\fR as the default 'make' command.
.TP 4
\fB\-\-no\-checksums\fR
Do not verify the checksum of downloaded archives.This is equivalent to setting \fB$OPAMNOCHECKSUMS\fR to "true".
.TP 4
\fB\-\-no\-switch\fR
Only install the compiler switch, without switching to it. If the compiler switch is already installed, then do nothing.
.TP 4
\fB\-\-no\-warning\fR
Do not display any warning related to environment variables.
.TP 4
\fB\-\-require\-checksums\fR
Reject the installation of packages that don't provide a checksum for the upstream archives. This is equivalent to setting \fB$OPAMREQUIRECHECKSUMS\fR to "true".
.TP 4
\fB\-s\fR, \fB\-\-short\fR
Output raw lists of names, one per line, skipping any details.
.TP 4
\fB\-\-show\-actions\fR
Call the solver and display the actions. Don't perform any changes.
.TP 4
\fB\-t\fR, \fB\-\-build\-test\fR
Build and \fBrun\fR the package unit\-tests. This is equivalent to setting \fB$OPAMBUILDTEST\fR to "true".
.SH COMMON OPTIONS
.P
These options are common to all commands.
.TP 4
\fB\-\-color\fR=\fIWHEN\fR (absent=auto)
Colorize the output. \fIWHEN\fR must be one of `always', `never' or `auto'.
.TP 4
\fB\-\-criteria\fR=\fICRITERIA\fR
Specify user \fIpreferences\fR for dependency solving for this run. Overrides both \fB$OPAMCRITERIA\fR and \fB$OPAMUPGRADECRITERIA\fR. For details on the supported language, and the external solvers available, see \fI http://opam.ocaml.org/doc/Specifying_Solver_Preferences.html\fR. A general guide to using solver preferences can be found at \fI http://www.dicosmo.org/Articles/usercriteria.pdf\fR. The default value is \-count(down),\-count(removed),\-notuptodate(solution),\-sum(solution,version\-lag),\-count(new) for upgrades, and \-count(removed),\-notuptodate(request),\-sum(request,version\-lag),\-count(down),\-notuptodate(changed),\-count(changed),\-notuptodate(solution),\-sum(solution,version\-lag) otherwise.
.TP 4
\fB\-\-cudf\fR=\fIFILENAME\fR
Debug option: Save the CUDF requests sent to the solver to \fIFILENAME\fR\-<n>.cudf.
.TP 4
\fB\-\-debug\fR
Print debug message to stderr. This is equivalent to setting \fB$OPAMDEBUG\fR to "true".
.TP 4
\fB\-\-debug\-level\fR=\fILEVEL\fR
Like `\-\-debug', but allows specifying the debug level (`\-\-debug' sets it to 1). Equivalent to setting \fB$OPAMDEBUG\fR to a positive integer.
.TP 4
\fB\-\-git\-version\fR
Print the git version if it exists and exit.
.TP 4
\fB\-\-help\fR[=\fIFMT\fR] (default=pager)
Show this help in format \fIFMT\fR (pager, plain or groff).
.TP 4
\fB\-\-no\-base\-packages\fR
Do not install base packages (useful for testing purposes). This is equivalent to setting \fB$OPAMNOBASEPACKAGES\fR to a non\-empty string.
.TP 4
\fB\-\-no\-self\-upgrade\fR
OPAM will replace itself with a newer binary found at \fBOPAMROOT/opam\fR if present. This disables this behaviour.
.TP 4
\fB\-q\fR, \fB\-\-quiet\fR
Be quiet when installing a new compiler.
.TP 4
\fB\-\-root\fR=\fIROOT\fR (absent=~/.opam)
Use \fIROOT\fR as the current root path. This is equivalent to setting \fB$OPAMROOT\fR to \fIROOT\fR.
.TP 4
\fB\-\-safe\fR
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.
.TP 4
\fB\-\-solver\fR=\fICMD\fR
Specify the name of the external dependency \fIsolver\fR. The default value is aspcud. Either 'aspcud', 'packup' or a custom command that may contain the variables %{input}%, %{output}% and %{criteria}%
.TP 4
\fB\-\-strict\fR
Fail whenever an error is found in a package definition or a configuration file. The default is to continue silently if possible.
.TP 4
\fB\-\-switch\fR=\fISWITCH\fR
Use \fISWITCH\fR as the current compiler switch. This is equivalent to setting \fB$OPAMSWITCH\fR to \fISWITCH\fR.
.TP 4
\fB\-\-use\-internal\-solver\fR, \fB\-\-no\-aspcud\fR
Force use of internal heuristics, even if an external solver is available.
.TP 4
\fB\-v\fR, \fB\-\-verbose\fR
Be more verbose, show package sub\-commands and their output. Repeat to see more. Repeating \fIn\fR times is equivalent to setting \fB$OPAMVERBOSE\fR to "\fIn\fR".
.TP 4
\fB\-\-version\fR
Show version information.
.TP 4
\fB\-y\fR, \fB\-\-yes\fR
Disable interactive mode and answer yes to all questions that would otherwise be asked to the user. This is equivalent to setting \fB$OPAMYES\fR to "true".
.SH ENVIRONMENT VARIABLES
.P
OPAM makes use of the environment variables listed here. Boolean variables should be set to "0", "no" of "false" to disable, "1", "yes" or "true" to enable.
.P
\fIOPAMCOLOR\fR, when set to \fIalways\fR or \fInever\fR, sets a default value for the \-\-color option.
.P
\fIOPAMCRITERIA\fR specifies user \fIpreferences\fR for dependency solving.The default value is \-count(removed),\-notuptodate(request),\-sum(request,version\-lag),\-count(down),\-notuptodate(changed),\-count(changed),\-notuptodate(solution),\-sum(solution,version\-lag). See also option \-\-criteria
.P
\fIOPAMCURL\fR can be used to select a given 'curl' program. See \fIOPAMFETCH\fR for more options.
.P
\fIOPAMDEBUG\fR see options `\-\-debug' and `\-\-debug\-level'.
.P
\fIOPAMDOWNLOADJOBS\fR sets the maximum number of simultaneous downloads.
.P
\fIOPAMEXTERNALSOLVER\fR see option `\-\-solver'.
.P
\fIOPAMFETCH\fR specifies how to download files: either `wget', `curl' or a custom command where variables \fB%{url}%\fR, \fB%{out}%\fR, \fB%{retries}%\fR, \fB%{compress}%\fR and \fB%{checksum}%\fR will be replaced. Overrides the 'download\-command' value from the main config file.
.P
\fIOPAMJOBS\fR sets the maximum number of parallel workers to run.
.P
\fIOPAMLOCKRETRIES\fR sets the number of tries after which OPAM gives up acquiring its lock and fails. <= 0 means infinite wait.
.P
\fIOPAMNO\fR answer no to any question asked.
.P
\fIOPAMNOASPCUD\fR see option `\-\-no\-aspcud'.
.P
\fIOPAMNOSELFUPGRADE\fR see option `\-\-no\-self\-upgrade'.
.P
\fIOPAMPINKINDAUTO\fR if set, version control systems are detected when pinning to a local path.
.P
\fIOPAMREQUIRECHECKSUMS\fR see option `\-\-require\-checksums'.
.P
\fIOPAMRETRY\fR sets the number of tries before failing downloads.
.P
\fIOPAMROOT\fR see option `\-\-root'. This is automatically set by `opam config env \-\-root=DIR' when DIR is non\-default or OPAMROOT is already defined.
.P
\fIOPAMSAFE\fR see option `\-\-safe'
.P
\fIOPAMSKIPVERSIONCHECKS\fR bypasses some version checks. Unsafe, for compatibility testing only.
.P
\fIOPAMSOLVERTIMEOUT\fR change the time allowance of the internal solver.
.P
\fIOPAMSTATUSLINE\fR display a dynamic status line showing what's currently going on on the terminal. (one of one of `always', `never' or `auto')
.P
\fIOPAMSWITCH\fR see option `\-\-switch'. Automatically set by `opam config env \-\-switch=SWITCH'.
.P
\fIOPAMUPGRADECRITERIA\fR specifies user \fIpreferences\fR for dependency solving when performing an upgrade. Overrides \fIOPAMCRITERIA\fR in upgrades if both are set.The default value is \-count(down),\-count(removed),\-notuptodate(solution),\-sum(solution,version\-lag),\-count(new). See also option \-\-criteria
.P
\fIOPAMUSEINTERNALSOLVER\fR see option `\-\-use\-internal\-solver'.
.P
\fIOPAMUTF8\fR use UTF8 characters in output (one of one of `always', `never' or `auto'). By default `auto', which is determined from the locale).
.P
\fIOPAMUTF8MSGS\fR use extended UTF8 characters (camels) in OPAM messages. Implies \fIOPAMUTF8\fR. This is set by default on OSX only.
.P
\fIOPAMVAR_var\fR overrides the contents of the variable \fIvar\fR when substituting `%{var}%` strings in `opam` files.
.P
\fIOPAMVAR_package_var\fR overrides the contents of the variable \fIpackage:var\fR when substituting `%{package:var}%` strings in `opam` files.
.P
\fIOPAMVERBOSE\fR see option `\-\-verbose'.
.P
\fIOPAMYES\fR see option `\-\-yes'.
.SH FURTHER DOCUMENTATION
.P
See https://opam.ocaml.org.
.SH AUTHORS
.P
Thomas Gazagnaire <thomas@gazagnaire.org>
.sp -1
.P
Anil Madhavapeddy <anil@recoil.org>
.sp -1
.P
Fabrice Le Fessant <Fabrice.Le_fessant@inria.fr>
.sp -1
.P
Frederic Tuong <tuong@users.gforge.inria.fr>
.sp -1
.P
Louis Gesbert <louis.gesbert@ocamlpro.com>
.sp -1
.P
Vincent Bernardoff <vb@luminar.eu.org>
.sp -1
.P
Guillem Rieu <guillem.rieu@ocamlpro.com>
.sp -1
.P
Roberto Di Cosmo <roberto@dicosmo.org>
.SH BUGS
.P
Check bug reports at https://github.com/ocaml/opam/issues.