.\" -*- mode: troff; coding: utf-8 -*-
.TH "nix3-log" "1" ""
.PP
\fBWarning\fR: This program is \fBexperimental\fR and its interface is subject to change.
.SH Name
\fCnix log\fR - show the build log of the specified packages or paths, if available
.SH Synopsis
\fCnix log\fR [\fIoption\fR\[u2026]] \fIinstallable\fR
.SH Examples
.IP "\(bu" 2
Get the build log of GNU Hello:
.LP
.EX
# nix log nixpkgs#hello
.EE
.IP "\(bu" 2
Get the build log of a specific store path:
.LP
.EX
# nix log /nix/store/lmngj4wcm9rkv3w4dfhzhcyij3195hiq-thunderbird-52.2.1
.EE
.IP "\(bu" 2
Get a build log from a specific binary cache:
.LP
.EX
# nix log --store https://cache.nixos.org nixpkgs#hello
.EE
.SH Description
This command prints the log of a previous build of the derivation
\fIinstallable\fR on standard output.
.PP
Nix looks for build logs in two places:
.IP "\(bu" 2
In the directory \fC/nix/var/log/nix/drvs\fR, which contains logs for
locally built derivations.
.IP "\(bu" 2
In the binary caches listed in the \fCsubstituters\fR setting. Logs
should be named \fC<cache>/log/<base-name-of-store-path>\fR, where
\fCstore-path\fR is a derivation,
e.g. \fChttps://cache.nixos.org/log/dvmig8jgrdapvbyxb1rprckdmdqx08kv-hello-2.10.drv\fR.
For non-derivation store paths, Nix will first try to determine the
deriver by fetching the \fC.narinfo\fR file for this store path.
.SH Options
\fBCommon evaluation options:\fR
.IP "\(bu" 2
\fC--arg\fR \fIname\fR \fIexpr\fR
.br
Pass the value \fIexpr\fR as the argument \fIname\fR to Nix functions.
.IP "\(bu" 2
\fC--argstr\fR \fIname\fR \fIstring\fR
.br
Pass the string \fIstring\fR as the argument \fIname\fR to Nix functions.
.IP "\(bu" 2
\fC--eval-store\fR \fIstore-url\fR
.br
The Nix store to use for evaluations.
.IP "\(bu" 2
\fC--impure\fR
.br
Allow access to mutable paths and repositories.
.IP "\(bu" 2
\fC--include\fR / \fC-I\fR \fIpath\fR
.br
Add \fIpath\fR to the list of locations used to look up \fC<...>\fR file names.
.IP "\(bu" 2
\fC--override-flake\fR \fIoriginal-ref\fR \fIresolved-ref\fR
.br
Override the flake registries, redirecting \fIoriginal-ref\fR to \fIresolved-ref\fR.
.LP
\fBCommon flake-related options:\fR
.IP "\(bu" 2
\fC--commit-lock-file\fR
.br
Commit changes to the flake\[u2019]s lock file.
.IP "\(bu" 2
\fC--inputs-from\fR \fIflake-url\fR
.br
Use the inputs of the specified flake as registry entries.
.IP "\(bu" 2
\fC--no-registries\fR
.br
Don\[u2019]t allow lookups in the flake registries. This option is deprecated; use \fC--no-use-registries\fR.
.IP "\(bu" 2
\fC--no-update-lock-file\fR
.br
Do not allow any updates to the flake\[u2019]s lock file.
.IP "\(bu" 2
\fC--no-write-lock-file\fR
.br
Do not write the flake\[u2019]s newly generated lock file.
.IP "\(bu" 2
\fC--override-input\fR \fIinput-path\fR \fIflake-url\fR
.br
Override a specific flake input (e.g. \fCdwarffs/nixpkgs\fR). This implies \fC--no-write-lock-file\fR.
.IP "\(bu" 2
\fC--recreate-lock-file\fR
.br
Recreate the flake\[u2019]s lock file from scratch.
.IP "\(bu" 2
\fC--update-input\fR \fIinput-path\fR
.br
Update a specific flake input (ignoring its previous entry in the lock file).
.LP
\fBOptions that change the interpretation of installables:\fR
.IP "\(bu" 2
\fC--derivation\fR
.br
Operate on the store derivation rather than its outputs.
.IP "\(bu" 2
\fC--expr\fR \fIexpr\fR
.br
Interpret installables as attribute paths relative to the Nix expression \fIexpr\fR.
.IP "\(bu" 2
\fC--file\fR / \fC-f\fR \fIfile\fR
.br
Interpret installables as attribute paths relative to the Nix expression stored in \fIfile\fR. If \fIfile\fR is the character -, then a Nix expression will be read from standard input.