We’ve all been there: a small shell script that starts as a quick helper suddenly becomes a critical part of your workflow. Then one day, it breaks - maybe because of a missing argument, a typo, or an unexpected input. Debugging at 2 AM isn’t fun. That’s why adding tests to your shell scripts is a lifesaver. With Bats (Bash Automated Testing System), you can catch these issues early and make your scripts as reliable as any other piece of software. ...
Sometimes this is useful for the diagnosis of configuration and network problems of ones Java application. This is our single-class HTTP client example without the need for external dependencies: HttpTest.java import javax.net.ssl.KeyManagerFactory; import javax.net.ssl.SSLContext; import javax.net.ssl.TrustManagerFactory; import java.io.FileInputStream; import java.io.IOException; import java.net.InetSocketAddress; import java.net.ProxySelector; import java.net.URI; import java.net.URISyntaxException; import java.net.http.HttpClient; import java.net.http.HttpRequest; import java.net.http.HttpRequest.BodyPublishers; import java.net.http.HttpResponse; import java.net.http.HttpResponse.BodyHandlers; import java.security.KeyManagementException; import java.security.KeyStore; import java.security.KeyStoreException; import java.security.NoSuchAlgorithmException; import java.security.UnrecoverableKeyException; import java.security.cert.CertificateException; import java.time.Duration; import java.time.temporal.ChronoUnit; public class HttpTest { public static void main(String[] args) throws URISyntaxException, NoSuchAlgorithmException, KeyManagementException, KeyStoreException, UnrecoverableKeyException, IOException, CertificateException { String bodyPayload = """ ourpayload, json, xml, ... """; String keyStorePath = "/opt/keystore.jks"; String keyStorePassword = "ABCDEFG"; String proxyHost = "ourproxy.proxy"; String uriString = "https://some-service/api"; int proxyPort = 8080; int timeoutInSeconds = 60; KeyStore keyStore = KeyStore.getInstance("JKS"); keyStore.load(new FileInputStream(keyStorePath), keyStorePassword.toCharArray()); KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance("PKIX"); keyManagerFactory.init(keyStore, null); TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance("PKIX"); // using same keystore for both trustManagerFactory.init(keyStore); SSLContext sslContext = SSLContext.getInstance("TLS"); sslContext.init(keyManagerFactory.getKeyManagers(), trustManagerFactory.getTrustManagers(), null); HttpClient client = HttpClient.newBuilder() .proxy( ProxySelector.of(new InetSocketAddress(proxyHost, proxyPort))) .sslContext(sslContext) .build(); URI uri = new URI(uriString); HttpRequest request = HttpRequest.newBuilder(uri) .POST(BodyPublishers.ofString(bodyPayload)) .timeout(Duration.of(timeoutInSeconds, ChronoUnit.SECONDS)) .build(); System.out.printf("Sending POST request to %s, timeout: %ds%n", uri, timeoutInSeconds); try { HttpResponse response = client.send(request, BodyHandlers.ofString()); System.out.println("Response received..."); System.out.printf("\tResponse-Status: %d%n", response.statusCode()); System.out.printf("\tResponse-Body: %s%n", response.body()); System.out.println("-------------------------------------%n"); } catch (IOException e) { System.err.printf("IOException caught: %s%n", e.getMessage()); e.printStackTrace(System.err); } catch (InterruptedException e) { System.err.printf("IOException caught: %s%n", e.getMessage()); e.printStackTrace(System.err); } } } ...
Managing my projects’ source code I am using Git also as Mercurial. Therefore I often encounter the situation where I am creating a special branch to implement a specific user story or feature request. Now when working on such a story branch I often enter the issue-key or a short title as a prefix for each commit message. Doing this by manually is a waste of time and error-prone and luckily for us, each of both DVCS offers us an easy API to add custom hooks to the different life-cycle events. ...
Restrict Network Can be useful when using a third-party image that we do not trust Run with no network docker run --network none <image> Run with private isolated network At least containers attached to this network can talk with another docker network create --internal my_isolated_network docker run --network my_isolated_network <image> Block using firewall e.g. using iptables or ipfw # Get container's IP docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' <container_name> # Block all outbound connections from that IP sudo iptables -I DOCKER-USER -s <container_ip> -j DROP ...
Show commits from another branch not contained in current branch git cherry -v otherbranch + f7d6a569bb6912aac97fce9ac92c4302863fb0d9 thecommit Create empty commit sometimes necessary for build/deploy pipelines … git commit --allow-empty -m "Empty-Commit" Cherry pick without commit git cherry-pick -n HASH Using vimdiff for diff set it via git config git config --global diff.tool vimdiff git config --global merge.tool vimdiff set it via ~/.gitconfig [diff] tool = vimdiff [merge] tool = vimdiff Using vscode as diff and mergetool You need to have the shell integration installed (code binary in PATH) ...
These are not only linux snippets but also bash snippets and snippets using tools that run under Linux, *nix or sometimes even MacOSX, I should reorder this article someday ;) Settings for more reliable bash scripts set -euo pipefail this gives us … -e: exit script if a single command fails -u: exit script if an unset variable is used -o pipefail: return value of a pipeline is the status of the last command to exit with a non-zero status, or zero if no command exited with a non-zero status ...
Ignore Namespaces in XPath Query e.g. Query for all xxx nodes ignoring their namespace: xmllint --xpath '//*[local-name()="xxx"]' input.xml An example parsing URLs from a sitemap XML. The URLs are located in //url/loc where all nodes are bound to the namespace http://www.sitemaps.org/schemas/sitemap/0.9. The following query ignores the namespace xmllint --xpath '//*[local-name()="url"]/*[local-name()="loc"]' sitemap.xml Pretty Print XML in the Console using xmllint echo '<blogs><blog url="https://www.hascode.com/">hasCode.com</blog></blogs>' | xmllint --format - <?xml version="1.0"?> <blogs> <blog url="https://www.hascode.com/">hasCode.com</blog> </blogs> ...