Spack Spec Command

The commands spack install and spack uninstall take a package name with an optional version of the package’s name. You can also specify the compiler, compiler version, architecture, compile options, and dependency options for a build. In Spack, that descriptor is called a spec. Spack uses specs to refer to a particular build configuration (or configurations) of a package.

For example, the following configuration is a spec of the tcl package.

If the above spec is provided to spack install command, it will install tcl package at version 8.6.10 using gcc compiler at version 9.2.1. Additionally, it says to link tcl with the zlib library (which it depends on) if it’s listed as a dependency of tcl. It also builds zlib with gcc@9.2.1 with the optimize option enabled.

Each spec must start with the package name (tcl). It also may consist of some optional pieces as shown in the following table:

For more details, visit Spack Documentation.

As mentioned above, a spec of a package should contain the package name and other optional pieces such as version, and compiler specifications. For example, you can install the zlib package as follows:

zlib is a spec that’s used to install zlib package. You can see that the version, compiler and its version, dependencies, variants, and flags are missing. In this case, the default spec will be used to install zlib.

The general syntax of spack spec command is:

The following table shows the options that can be used with spack spec command.

To find the spec that will be used to install the default version of the zlib package you can run spack spec as follows:

Output:

The output shows Input spec which is the spec that you type in the command line. Also, Concretized which is the concretized version of the Input spec. You can see in the concretized spec that the package version, compiler, and variants were specified.

To show the concretized spec of zlib@1.2.8 spec, you simply type:

Output:

Consider tcl as another example, you can find the concretized version of tcl using its hash. You first need to find its hash by typing:

Output:

From the above output, you can see that 3vbkxar is the hash of the installed package tcl. To find the spec of that package and show dependency hashes as well as versions using its hash, you type:

Output:

The above output shows the dependencies of the tcl package along with their hashes. You can also look at the spec of a dependency using its hash. To find the spec of zlib and check if it’s installed or not, you type:

The following output shows that the package has been installed [+].