arangosh Details

Interaction

You can paste multiple lines into arangosh, given the first line ends with an opening brace:

for (var i = 0; i < 10; i ++) {
  require("@arangodb").print("Hello world " + i + "!\n");
}
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To load your own JavaScript code into the current JavaScript interpreter context, use the load command:

require("internal").load("/tmp/test.js")

You can exit arangosh using the key combination <CTRL> + D or by typing quit<ENTER>.

Shell Output

The ArangoDB shell prints the output of the last evaluated expression by default:

42 * 23
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In order to prevent printing the result of the last evaluated expression, the expression result can be captured in a variable, e.g.

var calculationResult = 42 * 23
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There is also the print function to explicitly print out values in the ArangoDB shell:

print({ a: "123", b: [1,2,3], c: "test" });
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By default, the ArangoDB shell uses a pretty printer when JSON documents are printed. This ensures documents are printed in a human-readable way:

db._create("five")
for (i = 0; i < 5; i++) {
  db.five.save({value:i});
}
db.five.toArray()
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While the pretty-printer produces nice looking results, it needs a lot of screen space for each document. Sometimes a more dense output might be better. In this case, the pretty printer can be turned off using the command stop_pretty_print().

To turn on pretty printing again, use the start_pretty_print() command.

Escaping

In AQL, escaping is done traditionally with the backslash character: \. For literal backslashes, you need to double backslashes to \\. arangosh requires another level of escaping, also with the backslash character. It adds up to four backslashes that need to be written in arangosh for a single literal backslash (c:\tmp\test.js):

db._query('RETURN "c:\\\\tmp\\\\test.js"')

You can use bind variables to mitigate this:

var somepath = "c:\\tmp\\test.js"
db._query(aql`RETURN ${somepath}`)

Database Wrappers

arangosh provides the db object by default, and this object can be used for switching to a different database and managing collections inside the current database.

For a list of available methods for the db object, type

db._help();
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The db object is available in arangosh as well as on arangod i.e. if you’re using Foxx. While its interface is persistent between the arangosh and the arangod implementations, its underpinning is not. The arangod implementation are JavaScript wrappers around ArangoDB’s native C++ implementation, whereas the arangosh implementation wraps HTTP accesses to ArangoDB’s RESTful API.

So while this code may produce similar results when executed in arangosh and arangod, the CPU usage and time required differs since the arangosh version performs around 100k HTTP requests, and the arangod version directly writes to the database:

for (i = 0; i < 100000; i++) {
    db.test.save({ name: { first: "Jan" }, count: i});
}

Using arangosh via Unix shebang mechanisms

In Unix operating systems, you can start scripts by specifying the interpreter in the first line of the script. This is commonly called shebang or hash bang. You can also do that with arangosh, i.e. create ~/test.js:

#!/usr/bin/arangosh --javascript.execute 
require("internal").print("hello world")
db._query("FOR x IN test RETURN x").toArray()

Note that the first line has to end with a blank in order to make it work. Mark it executable to the OS:

> chmod a+x ~/test.js

and finally try it out:

> ~/test.js

Shell Configuration

arangosh looks for a user-defined startup script named .arangosh.rc in the user’s home directory on startup. The home directory is likely at /home/<username>/ on Unix/Linux.

If the file .arangosh.rc is present in the home directory, arangosh executes the contents of this file inside the global scope.

You can use this to define your own extra variables and functions that you need often. For example, you could put the following into the .arangosh.rc file in your home directory:

// "var" keyword avoided intentionally...
// otherwise "timed" would not survive the scope of this script
global.timed = function (cb) {
  console.time("callback");
  cb();
  console.timeEnd("callback");
};

This makes a function named timed available in arangosh in the global scope.

You can now start arangosh and invoke the function like this:

timed(function () { 
  for (var i = 0; i < 1000; ++i) {
    db.test.save({ value: i }); 
  }
});

Please keep in mind that, if present, the .arangosh.rc file needs to contain valid JavaScript code. If you want any variables in the global scope to survive you need to omit the var keyword for them. Otherwise, the variables are only visible inside the script itself, but not outside.

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