# How do you find documentation of -j option
**URL:** https://discourse.cmake.org/t/how-do-you-find-documentation-of-j-option/2561
**Category:** Usage
**Created:** [January 17, 2021, 4:31am UTC](https://discourse.cmake.org/t/how-do-you-find-documentation-of-j-option/2561 "2021-01-17T04:31:51Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@pauljurczak](https://discourse.cmake.org/u/pauljurczak)
#### Post date: [January 17, 2021, 4:31am UTC](https://discourse.cmake.org/t/how-do-you-find-documentation-of-j-option/2561/1 "2021-01-17T04:31:51Z")
AFAIK, `cmake --build -j .` is a legal command, but I can’t find documentation for `-j` option. I tried:
```auto
cmake --help | grep -- "-j"
cmake --help-command build_command | grep -- "-j"
```
as well as searching for `-j` and `option -j` on [https://cmake.org/cmake/help/latest/search.html?q=q=option+j](https://cmake.org/cmake/help/latest/search.html?q=q=option+j) without success.
---
### Author:  [@McMartin](https://discourse.cmake.org/u/McMartin)
#### Post date: [January 17, 2021, 8:42am UTC](https://discourse.cmake.org/t/how-do-you-find-documentation-of-j-option/2561/2 "2021-01-17T08:42:31Z")
I think `cmake --build . --help` gives the usage of the “Build a Project” mode, which is also documented here: [https://cmake.org/cmake/help/latest/manual/cmake.1.html#build-a-project](https://cmake.org/cmake/help/latest/manual/cmake.1.html#build-a-project)
---
### Author:  [@anon45792294](https://discourse.cmake.org/u/anon45792294)
#### Post date: [January 17, 2021, 12:14pm UTC](https://discourse.cmake.org/t/how-do-you-find-documentation-of-j-option/2561/3 "2021-01-17T12:14:39Z")
From the cmake docs ([https://cmake.org/cmake/help/latest/manual/cmake.1.html](https://cmake.org/cmake/help/latest/manual/cmake.1.html))
```auto
`--parallel [], -j []`
The maximum number of concurrent processes to use when building. If `` is omitted the native build tool’s default number is used.
The [`CMAKE_BUILD_PARALLEL_LEVEL`](https://cmake.org/cmake/help/latest/envvar/CMAKE_BUILD_PARALLEL_LEVEL.html#envvar:CMAKE_BUILD_PARALLEL_LEVEL) environment variable, if set, specifies a default parallel level when this option is not given.
Some native build tools always build in parallel. The use of `` value of `1` can be used to limit to a single job.
```
---
### Author:  [@pauljurczak](https://discourse.cmake.org/u/pauljurczak)
#### Post date: [January 17, 2021, 7:33pm UTC](https://discourse.cmake.org/t/how-do-you-find-documentation-of-j-option/2561/4 "2021-01-17T19:33:58Z")
Thanks. It would be nice though, if `-j` was discoverable through the search engine. I’m not sure if it can be configured to successfully handle queries like that.
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### Author:  [@pauljurczak](https://discourse.cmake.org/u/pauljurczak)
#### Post date: [January 17, 2021, 7:35pm UTC](https://discourse.cmake.org/t/how-do-you-find-documentation-of-j-option/2561/5 "2021-01-17T19:35:53Z")
`cmake --build . --help` works great. I didn’t know you can use `--help` option that far to the right.
---
### Author:  [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)
#### Post date: [January 19, 2021, 7:43pm UTC](https://discourse.cmake.org/t/how-do-you-find-documentation-of-j-option/2561/6 "2021-01-19T19:43:54Z")
> [@pauljurczak](#):
>
> It would be nice though, if `-j` was discoverable through the search engine. I’m not sure if it can be configured to successfully handle queries like that.
It’s a victim of the short search query (single letter) and having search syntax attached to it (the hyphen). For things like this, doing a raw text search (on the repo or the raw HTML files if you have the source or docs handy) using `grep` or similar tools is how I usually handle it.