Network Basics (ping, wget, curl)

Category: Linux Command Basics
Type: Linux Commands
Generated on: 2025-07-10 03:07:23
For: System Administration, Development & Technical Interviews

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Network Basics Cheatsheet (ping, wget, curl) - Linux Commands

This cheatsheet provides a comprehensive guide to ping, wget, and curl, essential commands for network troubleshooting and data transfer in Linux.

1. Command Overview

• ping: Tests network connectivity by sending ICMP “echo request” packets to a target host and waiting for “echo reply” packets. Used to verify if a host is reachable.
• wget: Downloads files from the web using HTTP, HTTPS, and FTP protocols. Useful for retrieving files, mirroring websites, and scheduling downloads.
• curl: A versatile command-line tool for transferring data with URLs. Supports a wide range of protocols (HTTP, HTTPS, FTP, SMTP, etc.) and is commonly used for interacting with APIs, testing web services, and downloading files.

2. Basic Syntax

• ping:

  ping [options] <hostname or IP address>

• wget:

  wget [options] <URL>

• curl:

  curl [options] <URL>

3. Practical Examples

• ping:

  • Basic connectivity test:

    ping google.com

    PING google.com (142.250.184.142) 56(84) bytes of data.
    64 bytes from fra16s31-in-f14.1e100.net (142.250.184.142): icmp_seq=1 ttl=117 time=7.31 ms
    64 bytes from fra16s31-in-f14.1e100.net (142.250.184.142): icmp_seq=2 ttl=117 time=7.25 ms
    ^C
    --- google.com ping statistics ---
    2 packets transmitted, 2 received, 0% packet loss, time 1001ms
    rtt min/avg/max/mdev = 7.253/7.282/7.312/0.029 ms

  • Ping a specific IP address:

    ping 8.8.8.8

• wget:

  • Download a file:

    wget https://example.com/file.txt

    This will download file.txt to the current directory.

  • Download a file with a different name:

    wget -O new_file.txt https://example.com/file.txt

• curl:

  • Download a file and display its contents in the terminal:

    curl https://example.com/index.html

    This will print the HTML source code of index.html to the standard output.

  • Download a file and save it to a file:

    curl -o index.html https://example.com/index.html

    This will download index.html and save it as index.html in the current directory.

  • Make a simple GET request to an API:

    curl https://api.example.com/users

    This will retrieve user data from the API.

4. Common Options

• ping:

  • -c <count>: Stop after sending <count> ECHO_REQUEST packets. Example: ping -c 5 google.com (sends 5 pings).
  • -i <interval>: Wait <interval> seconds between sending each packet. Example: ping -i 2 google.com (sends pings every 2 seconds).
  • -s <size>: Specify the packet size. Example: ping -s 1024 google.com (sends 1024-byte packets).
  • -t <ttl>: Set the Time To Live (TTL) value. Example: ping -t 64 google.com (sets TTL to 64).
  • -w <deadline>: Specify a timeout, in seconds, before ping exits regardless of how many packets have been sent or received.

• wget:

  • -O <filename>: Specify the output filename. Example: wget -O myfile.zip https://example.com/file.zip
  • -q: Quiet mode (suppress output). Example: wget -q https://example.com/file.txt
  • -c: Continue an interrupted download. Example: wget -c https://example.com/largefile.iso
  • -b: Run in the background. Example: wget -b https://example.com/file.txt
  • -r: Recursive download (download entire website). WARNING: Use with caution. Can consume significant bandwidth and storage. Example: wget -r https://example.com
  • -l <level>: Set the recursion depth. Example: wget -r -l 2 https://example.com (download up to 2 levels deep).
  • --limit-rate=<rate>: Limits the download rate. Example: wget --limit-rate=200k https://example.com/largefile.iso (limits to 200 KB/s)
  • --no-check-certificate: Don’t verify the server’s certificate. Use with caution. Example: wget --no-check-certificate https://self-signed.example.com

• curl:

  • -o <filename>: Specify the output filename. Example: curl -o myfile.html https://example.com/index.html
  • -O: Use the remote file name for saving the downloaded file. Example: curl -O https://example.com/myfile.zip
  • -I: Get only the headers of the response. Example: curl -I https://example.com (useful for checking server status and headers).
  • -v: Verbose mode (show more details about the transfer). Example: curl -v https://example.com
  • -H <header>: Add a custom header to the request. Example: curl -H "Content-Type: application/json" https://api.example.com/data
  • -X <method>: Specify the HTTP method (GET, POST, PUT, DELETE, etc.). Example: curl -X POST -d '{"key":"value"}' https://api.example.com/data
  • -d <data>: Send data in a POST request. Example: curl -d "param1=value1&param2=value2" https://api.example.com/submit
  • --data-binary <data>: Send binary data in a POST request. Useful for sending files. Example: curl --data-binary @myfile.txt https://api.example.com/upload
  • -u <user:password>: Specify the username and password for authentication. Example: curl -u user:password https://example.com/protected
  • -k: Allow insecure server connections (don’t verify SSL certificates). WARNING: Use with caution. Can expose you to security risks. Example: curl -k https://self-signed.example.com
  • --limit-rate <rate>: Limits the transfer rate. Example: curl --limit-rate 100k https://example.com/largefile.iso (limits to 100 KB/s)

5. Advanced Usage

• ping:

  • Scripting:

    #!/bin/bash
    if ping -c 1 google.com > /dev/null 2>&1; then
      echo "Google is reachable"
    else
      echo "Google is not reachable"
    fi

  • Measuring Latency:

    ping -c 10 google.com | awk '/time=/{print $7}' | cut -d '=' -f 2 | awk '{sum += $1; n++} END {if (n > 0) print sum / n}'

    This script calculates the average latency from 10 pings to google.com.

• wget:

  • Downloading multiple files from a list:

    Create a file named urls.txt with a list of URLs, one URL per line.

    wget -i urls.txt

  • Mirroring a website (advanced):

    wget -mkEpnp https://example.com

    • -m: Mirroring (recursive download with timestamping).
    • -k: Convert links to be relative, for local viewing.
    • -E: Append .html to HTML files.
    • -p: Get all images, CSS, etc. needed to display HTML pages properly.
    • -n: Use timestamping (don’t re-download files that haven’t changed).

    WARNING: This can download a significant amount of data. Use with caution.

• curl:

  • Uploading a file using POST:

    curl -F "file=@myfile.txt" https://api.example.com/upload

  • Sending JSON data to an API:

    curl -H "Content-Type: application/json" -X POST -d '{"key":"value"}' https://api.example.com/api_endpoint

  • Following redirects:

    curl -L https://example.com/shorturl

    -L follows redirects. Useful for handling shortened URLs.

  • Using cookies:

    • Saving cookies:

      curl -c cookies.txt https://example.com/login

    • Sending cookies:

      curl -b cookies.txt https://example.com/protected

  • Using proxies:

    curl -x <proxy_address:port> https://example.com

    Example: curl -x http://proxy.example.com:8080 https://example.com

  • Using authentication with API keys:

    curl -H "Authorization: Bearer YOUR_API_KEY" https://api.example.com/resource

6. Tips & Tricks

• ping:

  • Use Ctrl+C to stop ping.
  • Pinging the gateway IP address is a quick way to check local network connectivity.

• wget:

  • Combine -b and -c for background downloads that can be resumed.
  • Use nohup wget <URL> & for persistent background downloads that survive terminal closure.
  • Consider --waitretry to retry failed downloads after a specified interval.

• curl:

  • Use jq to pretty-print JSON responses: curl https://api.example.com | jq . (requires jq to be installed).
  • Use -w to get transfer information like time, speed, and size.

    curl -s -w 'Time: %{time_total}s\nSpeed: %{speed_download} bytes/s\nSize: %{size_download} bytes\n' -o /dev/null https://example.com

  • For complex POST requests, create a JSON file and use --data @filename.json.

7. Troubleshooting

• ping:

  • “Destination Host Unreachable”: The target host is not reachable from your network. Check network configuration, DNS resolution, and firewall rules.
  • “Request timed out”: The target host is reachable, but not responding to ICMP requests within the timeout period. This could be due to a firewall blocking ICMP, network congestion, or the host being overloaded.
  • If pinging a hostname fails, but pinging the IP address works, there’s likely a DNS resolution issue. Check your /etc/resolv.conf file.

• wget:

  • “Connection refused”: The target server is refusing the connection. This could be due to the server being down, a firewall blocking the connection, or an incorrect port number.
  • “404 Not Found”: The requested resource does not exist on the server. Double-check the URL.
  • “Certificate verification failed”: The SSL certificate of the server is not trusted. Use --no-check-certificate (with caution) or ensure that the CA certificate is installed on your system.
  • “Failed to write to disk”: Check disk space and permissions.

• curl:

  • “curl: (7) Failed to connect to host”: The target host is unreachable. Check network connectivity, DNS resolution, and firewall rules. Similar to ping’s “Destination Host Unreachable”.
  • “curl: (60) SSL certificate problem”: The SSL certificate of the server is not trusted. Use -k (with caution) or ensure that the CA certificate is installed on your system.
  • “400 Bad Request”: The server cannot understand the request due to invalid syntax or parameters. Check the request format, headers, and data.
  • “401 Unauthorized”: Authentication is required. Provide the correct credentials using -u or appropriate API key headers.
  • “403 Forbidden”: The server understands the request, but refuses to fulfill it. This usually indicates that the client does not have the necessary permissions.
  • If getting intermittent errors, check the server’s logs for more details.

8. Related Commands

• traceroute / tracepath: Trace the route packets take to a destination.
• nslookup / dig: Query DNS servers to resolve domain names.
• netstat / ss: Display network connections, routing tables, and interface statistics.
• tcpdump / wireshark: Capture and analyze network traffic.
• scp / rsync: Securely copy files between systems.
• nc (netcat): A versatile tool for reading from and writing to network connections.
• host: DNS lookup utility.