Bash和MongoDB：Eval中的空白不起作用

Question

In a bash script, this won't work with Unexpected token ILLEGAL

#!/bin/bash
value="White Spaced String"
mongo --verbose localhost:27017/myDB --eval 'db.ips.update({"id":"id"}, { $push: { "key": {"key":"'$value'"}}})'

where as this works:

#!/bin/bash
value="NonWhiteSpacedString"
mongo --verbose localhost:27017/myDB --eval 'db.ips.update({"id":"id"}, { $push: { "key": {"key":"'$value'"}}})'

Any ideas ow to work around this? I tried:

value="${value// /\\\\ }" which will substitute whitespaces with \\ escape signs and a whitespace. Yet, no success.

This does work, yet I want to preserve the whitespaces in my JSON in Mongo:

value="${value// /_}"

Answer 1

The argument to the --eval option needs to be a single bash word, so you need to avoid bash word-expanding $value . That means you need to put the expansion inside double-quotes:

mongo --verbose localhost:27017/myDB --eval \
  'db.ips.update({"id":"id"}, { $push: { "key": {"key":"'"$value"'"}}})'
                                                         ^      ^

That argument consists of a single-quoted segment, a double-quoted segment, and then a final single-quoted segment. The double quotes inside the single-quoted segments are, of course, ordinary characters.