This is just a quick post for reference as I had issues installing jq on my machine this evening.

$ brew install jq
==> Installing dependencies for jq: oniguruma
==> Installing jq dependency: oniguruma
==> Downloading https://homebrew.bintray.com/bottles/oniguruma-5.9.6.el_capitan.bottle.1.tar.gz
######################################################################## 100.0%
==> Pouring oniguruma-5.9.6.el_capitan.bottle.1.tar.gz
Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
Could not symlink include/oniggnu.h
/usr/local/include is not writable.

You can try again using:
  brew link oniguruma
==> Summary
🍺  /usr/local/Cellar/oniguruma/5.9.6: 12 files, 1M
==> Installing jq
==> Downloading https://homebrew.bintray.com/bottles/jq-1.5.el_capitan.bottle.1.tar.gz
######################################################################## 100.0%
==> Pouring jq-1.5.el_capitan.bottle.1.tar.gz
Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
Could not symlink include/jq.h
/usr/local/include is not writable.

You can try again using:
  brew link jq
==> Summary
🍺  /usr/local/Cellar/jq/1.5: 17 files, 953.3K

Following the suggestion, I tried to link jq:

$ brew link jq
Linking /usr/local/Cellar/jq/1.5...
Error: Could not symlink lib/libjq.1.dylib
/usr/local/lib is not writable.

No luck. So I made /usr/local/lib writeable by my user and then retried:

$ sudo chown -R $(whoami) /usr/local/lib
$ brew link jq
Linking /usr/local/Cellar/jq/1.5... 8 symlinks created

That seemed to have worked, but when I tried to run a jq command I hit more errors:

$ vault read -format=json secret/baz | jq -r .data.value
dyld: Library not loaded: /usr/local/lib/libonig.2.dylib
  Referenced from: /usr/local/bin/jq
  Reason: image not found
Trace/BPT trap: 5

So I tried removing jq and starting again:

$ brew remove jq
Uninstalling /usr/local/Cellar/jq/1.5... (17 files, 953.3K)
$ brew install jq
Error: You must `brew link oniguruma` before jq can be installed

Fine.

$ brew link oniguruma
Linking /usr/local/Cellar/oniguruma/5.9.6... 8 symlinks created

Third time lucky…

$ brew install jq
==> Downloading https://homebrew.bintray.com/bottles/jq-1.5.el_capitan.bottle.1.tar.gz
Already downloaded: /Library/Caches/Homebrew/jq-1.5.el_capitan.bottle.1.tar.gz
==> Pouring jq-1.5.el_capitan.bottle.1.tar.gz
🍺  /usr/local/Cellar/jq/1.5: 17 files, 953.3K

Woot. Fingers crossed…

$vault read -format=json secret/baz | jq -r .data.value
bar

Just in case you run into the same issue :-)