Ninja not found by CMake

My solution: symlink "ninja-build" to "ninja".

# ln -s /usr/bin/ninja /usr/bin/ninja-build

This only works on very old versions of CMake, which I will explain below.

I had already dropped my fresh "ninja" binary into /usr/bin and checked it had 0755 permissions. I was stumped until I ran an strace on the generator command.

# strace cmake -GNinja .. | grep -i ninja
access("ninja-build", R_OK)             = -1 ENOENT (No such file or directory)
access("/usr/local/sbin/ninja-build", R_OK) = -1 ENOENT (No such file or directory)
access("/usr/local/bin/ninja-build", R_OK) = -1 ENOENT (No such file or directory)
access("/sbin/ninja-build", R_OK)       = -1 ENOENT (No such file or directory)
access("/bin/ninja-build", R_OK)        = -1 ENOENT (No such file or directory)
access("/usr/sbin/ninja-build", R_OK)   = -1 ENOENT (No such file or directory)
access("/usr/bin/ninja-build", R_OK)    = -1 ENOENT (No such file or directory)
access("/opt/texlive/2016/bin/i386-linux/ninja-build", R_OK) = -1 ENOENT (No such file or directory)
access("/root/bin/ninja-build", R_OK)   = -1 ENOENT (No such file or directory)

It was looking for "ninja-build", not "ninja"!

I use CMake with Ninja extensively at work and at home, on Windows and Linux. So why haven't I seen this bug before?

Well... in this instance I'm using a very old version of CMake, version 2.8.12. It's so old it's almost fossilised. So presumably it's either a CMake bug which was fixed later, or the Ninja project changed the name of the binary at some point.

In Debian/Ubuntu systems, go ahead and install it

apt install ninja-build

Then rerun CMake.

If ninja really exists in $PATH and it still does not work, you should check the permission of the executable file via ls -l /PATH/TO/NINJA. Make sure others have read and execute permissions (like '-rwxr-xr-x').

See also: 0013910: Ninja generator initialization fails if /usr/bin/ninja is not world-readable

The script you are executing uses the CMake Ninja generator. For that to work you need Ninja on the path. On most Linux distributions you can install it from a package.

Ubuntu: ninja-build

openSUSE: ninja

If you can't find it for your distribution, you have to download it and add its location to the path environment variable.