I'm working on a project where Nodejs is used for the backend and redis is used for caching application data. Here's an example of making a shell command to delete redis cache keys using child_process exec and promisify. I find it easier (and more intuitive) to use async/await than to use callbacks.
Environment:
CentOS Linux release 7.3.1611 (Core)
node v14.9.0
// child process currently doesn't natively support promises, however can wrap the
// methods with promises using built-in promisify util
const { promisify } = require("util");
const execAsync = promisify(require("child_process").exec);
/**
* Deletes all keys from cache that start with cacheCode param. If
* cacheCode is not defined, deletes all cache.
* @param {String} cacheCode.
* @throws {Error}
* @returns {String} how many keys effected
*/
async function flushFromCache(cacheCode) {
const pattern = cacheCode ? ` --pattern ${cacheCode}_*` : "";
const command = `redis-cli --scan${pattern} | xargs redis-cli del`;
try {
const execResult = await execAsync(command);
// result looks like { stdout: string, stderr: string }.
// stdout is populated when everything goes nicely.
// stderr is populated if error occurred while running command
if (execResult.stderr) {
throw new Error(execResult.stderr);
}
// When there are keys deleted the result looks like:
// (integer) 2
// When there are no keys found the result looks like:
// ERR wrong number of arguments for 'del' command
let result;
if (execResult.stdout.includes("ERR")) {
result = `No ${cacheCode ? `'${cacheCode}'` : ""} keys to flush`;
} else {
result = `${execResult.stdout.trim()} ${
cacheCode ? `'${cacheCode}'` : ""
} keys flushed`;
}
return result;
} catch (e) {
// this error can occur if the command is bad
throw new Error(e.message);
}
}
module.exports = {
flushFromCache
};
These articles were helpful:
https://stackabuse.com/executing-shell-commands-with-node-js/
https://stackoverflow.com/questions/20643470/execute-a-command-line-binary-with-node-js