Mastering Linux: How to Install and Use ‘Curl’ Command

Are you looking to install the curl command on your Linux system but aren’t sure where to start? Many Linux users, particularly beginners, might find the task daunting. Yet, installing curl will make it easy to download resources from the web via the Linux command line. Curl is also readily available on most package management systems, making it a straightforward process once you know-how.

In this tutorial, we will guide you on how to install the curl command on your Linux system. We will show you methods for both APT and YUM-based distributions, delve into compiling curl from source, installing a specific version, and finally, how to use the curl command and ensure it’s installed correctly.

So, let’s dive in and begin installing curl on your Linux system!

TL;DR: How Do I Install the ‘curl’ Command in Linux?

Most Linux distributions come with 'curl' pre-installed. However, if it’s not, you can install it using your distribution’s package manager with the syntax, sudo [apt/yum] install curl. You can also verify its installation with, curl --version.

For example, on Debian-based distributions like Ubuntu, use the command:

sudo apt-get install curl

For RPM-based distributions like CentOS, use the command:

sudo yum install curl

# Output:
# 'curl is already the newest version (7.58.0-2ubuntu3.13).'
# '0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.'

This is a basic way to install the curl command in Linux, but there’s much more to learn about installing and using curl. Continue reading for more detailed information and advanced usage scenarios.

Understanding the ‘curl’ Command in Linux

Before we dive into the installation process, it’s essential to understand what the ‘curl’ command is and why it’s beneficial. ‘curl’ stands for ‘Client URL.’ It’s a command-line utility used to transfer data to or from a network server, using one of the supported protocols (HTTP, HTTPS, FTP, and more). It’s a powerful tool for testing, downloading files, or even debugging network-related issues.

Now, let’s get to the installation part.

Installing ‘curl’ with APT

For Debian-based distributions like Ubuntu, we’ll use the Advanced Packaging Tool (APT) to install ‘curl’. Here’s how to do it:

sudo apt update
sudo apt install curl

# Output:
# 'Reading package lists... Done'
# 'Building dependency tree'
# 'Reading state information... Done'
# 'curl is already the newest version (7.58.0-2ubuntu3.13).'
# '0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.'

This output indicates that ‘curl’ is already installed and is the newest version. If ‘curl’ wasn’t installed, this command would install it for you.

Installing ‘curl’ with YUM

For RPM-based distributions like CentOS, we’ll use the Yellowdog Updater, Modified (YUM) to install ‘curl’. Here’s how:

sudo yum update
sudo yum install curl

# Output:
# 'Loaded plugins: fastestmirror, ovl'
# 'Loading mirror speeds from cached hostfile'
# '* base: mirrors.tuna.tsinghua.edu.cn'
# 'Package curl-7.29.0-59.el7_9.1.x86_64 already installed and latest version'
# 'Nothing to do'

This output tells you that ‘curl’ is already installed and is the latest version. If ‘curl’ wasn’t installed, this command would install it for you.

Installing ‘curl’ with DNF

For Fedora, we’ll use Dandified YUM (DNF) to install ‘curl’. Here’s how:

sudo dnf check-update
sudo dnf install curl

# Output:
# 'Last metadata expiration check: 0:03:14 ago on Mon 24 Jan 2022 04:42:15 PM CET.'
# 'Package curl-7.76.1-2.fc34.x86_64 is already installed.'
# 'Dependencies resolved.'
# 'Nothing to do.'
# 'Complete!'

This output signifies that ‘curl’ is already installed. If it wasn’t, this command would install it.

In the next section, we’ll dive into more advanced uses of the ‘curl’ command.

Installing ‘curl’ from Source Code

Sometimes, you may need to install ‘curl’ from the source code. This could be due to the need for a specific version not available in your distribution’s package repository or to enable certain features. Here’s how you can do this:

# Download the latest curl version from the official site
wget https://curl.se/download/curl-7.79.1.tar.gz

# Extract the downloaded file
 tar -xvf curl-7.79.1.tar.gz

# Change directory to the extracted folder
 cd curl-7.79.1

# Run the configure script
./configure

# Compile the source code
make

# Install curl
sudo make install

# Output:
# 'curl is successfully installed from source'

Installing Different Versions of ‘curl’

Installing from Source

To install a specific version of ‘curl’ from source, you only need to modify the download URL in the first step of the previous section with the URL of the desired version.

Using Package Managers

To install a specific version of ‘curl’ using apt or yum, you can specify the version number in the installation command. Here’s how:

Using APT

sudo apt-get install curl=7.58.0-2ubuntu3.13

# Output:
# 'curl (7.58.0-2ubuntu3.13) is being installed.'

Using YUM

sudo yum install curl-7.29.0-59.el7_9.1.x86_64

# Output:
# 'curl (7.29.0-59.el7_9.1.x86_64) is being installed.'

Different versions of ‘curl’ might have different features or bug fixes. It’s important to choose a version that fits your needs. Here’s a comparison of some versions:

Using and Verifying ‘curl’

Basic Usage of ‘curl’

The most basic use of ‘curl’ is to download a file from a website. Here’s an example:

curl -O https://example.com/file.txt

# Output:
# 'file.txt has been downloaded.'

Verifying ‘curl’ Installation

To verify that ‘curl’ is installed correctly, you can use the following command:

curl --version

# Output:
# 'curl 7.58.0 (x86_64-pc-linux-gnu) libcurl/7.58.0 OpenSSL/1.1.1 zlib/1.2.11 libidn2/2.0.4 libpsl/0.19.1 (+libidn2/2.0.4) nghttp2/1.30.0 librtmp/2.3'

This command will print the installed ‘curl’ version and some information about the features enabled in the build. If ‘curl’ is installed correctly, you should see output similar to the above.

Exploring Alternatives to ‘curl’ in Linux

While ‘curl’ is a powerful tool for downloading files from the web, Linux offers alternative methods that might better suit your needs. One such method is the ‘wget’ command.

Understanding the ‘wget’ Command

‘wget’ is a free utility for non-interactive download of files from the web. It supports HTTP, HTTPS, and FTP protocols, and can retrieve files through HTTP proxies.

Here’s a basic example of downloading a file using ‘wget’:

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

# Output:
# '--2022-01-25 12:00:00--  https://example.com/file.txt'
# 'Resolving example.com (example.com)... 93.184.216.34, 2606:2800:220:1:248:1893:25c8:1946'
# 'Connecting to example.com (example.com)|93.184.216.34|:443... connected.'
# 'HTTP request sent, awaiting response... 200 OK'
# 'Length: unspecified [text/plain]'
# 'Saving to: ‘file.txt’'

# 'file.txt            [ <=>                ]   4.41K  --.-KB/s    in 0s      '

# '2022-01-25 12:00:00 (39.7 MB/s) - ‘file.txt’ saved [4512]'

In this example, ‘wget’ downloads the file and saves it with the original file name.

‘curl’ vs. ‘wget’

While both ‘curl’ and ‘wget’ are used for downloading files, they have some differences:

• ‘curl’ supports more protocols than ‘wget’.
• ‘wget’ can download files recursively, which ‘curl’ cannot do.
• ‘curl’ can transfer data to or from a server, while ‘wget’ can only download files.

Here’s a comparison table for quick reference:

In conclusion, ‘curl’ and ‘wget’ are both powerful tools for downloading files in Linux. Your choice between them depends on your specific needs. If you need to interact with a server or require support for a protocol not supported by ‘wget’, ‘curl’ is your best bet. However, if you need to download files recursively, ‘wget’ would be the better option.

Troubleshooting ‘curl’ Installation and Usage

Even with the most straightforward tools, you might encounter issues or errors. Here, we’ll discuss common problems you may face when installing or using the ‘curl’ command in Linux and how to resolve them.

‘curl’ Command Not Found

If you see a ‘curl: command not found’ error, it means ‘curl’ is not installed on your system. You can resolve this by installing ‘curl’ using the methods discussed earlier in this guide.

SSL Certificate Errors

When using ‘curl’ to download files from a website using HTTPS, you might encounter SSL certificate errors. This can occur if the website’s SSL certificate is self-signed, expired, or issued by an untrusted certificate authority. To bypass this, you can use the -k or --insecure option with ‘curl’. However, be aware this is not recommended for sensitive data as it bypasses the SSL security.

curl -k https://self-signed.badssl.com/

# Output:
# '<!DOCTYPE html>
# <html>
# <head>
# ...'

In this example, ‘curl’ successfully retrieves the content of the webpage with a self-signed SSL certificate.

Slow Download Speed

If you’re experiencing slow download speeds with ‘curl’, it could be due to network congestion or a slow server. You can use the -Y and -y options to set the minimum download speed and the time ‘curl’ should wait before aborting the download.

curl -O -Y 1000 -y 20 https://example.com/big-file.zip

# Output:
# 'big-file.zip has been downloaded.'

In this example, ‘curl’ will abort the download if the speed drops below 1000 bytes per second for 20 seconds.

Verbose Mode for Debugging

If you’re having trouble with a ‘curl’ command, you can use the -v or --verbose option to get more information about what ‘curl’ is doing. This can help you pinpoint the problem.

curl -v https://example.com

# Output:
# '*   Trying 93.184.216.34:80...'
# '* Connected to example.com (93.184.216.34) port 80 (#0)'
# 'GET / HTTP/1.1'
# 'Host: example.com'
# 'User-Agent: curl/7.58.0'
# 'Accept: */*'
# '...'

In this example, ‘curl’ provides detailed information about the connection and the HTTP request.

Remember, the ‘curl’ command is a versatile tool with many options and features. Don’t be afraid to explore the man pages (man curl) or use the --help option (curl --help) to learn more about what ‘curl’ can do.

Understanding ‘curl’ and its Importance in Linux

The ‘curl’ command is a vital tool in the Linux ecosystem. But what exactly is ‘curl’, and why is it so important?

What is ‘curl’?

‘curl’ stands for ‘Client URL.’ It’s a command-line tool used for transferring data to or from a server, using one of the supported protocols. These protocols include HTTP, HTTPS, FTP, IMAP, SMTP, and more. This wide range of supported protocols makes ‘curl’ a versatile tool for any Linux user.

Here’s an example of how ‘curl’ can be used to send a GET request to a website:

curl https://example.com

# Output:
# '<!DOCTYPE html>
# <html>
# <head>
# ...'

In this example, ‘curl’ sends a GET request to ‘example.com’ and prints the HTML content of the webpage to the terminal.

Why is ‘curl’ Important?

‘curl’ is important for several reasons. First, it supports a wide range of protocols, making it a one-stop tool for many network-related tasks. Whether you’re downloading a file, testing an API, or sending an email, ‘curl’ can handle it.

Second, ‘curl’ is non-interactive, meaning it can run without user intervention. This makes ‘curl’ a great tool for automation and scripting.

Finally, ‘curl’ is open-source and widely supported. It’s available on almost all Linux distributions, and there’s a wealth of tutorials and resources available to help you master it.

Understanding Protocols and ‘curl’

A network protocol is a set of rules for how data is transmitted over a network. ‘curl’ supports many network protocols, each with its own unique features and use cases.

For example, HTTP and HTTPS are used for web browsing, FTP for file transfer, SMTP for sending email, and so on. ‘curl’ can interact with these protocols directly from the command line, providing a powerful interface for network communication.

Here’s an example of using ‘curl’ to send an email via SMTP:

curl --mail-from [email protected] --mail-rcpt [email protected] --url smtp://smtp.example.com --upload-file mail.txt

# Output:
# 'Mail sent successfully'

In this example, ‘curl’ sends an email from ‘[email protected]’ to ‘[email protected]’ using the SMTP server ‘smtp.example.com’. The content of the email is read from the file ‘mail.txt’.

In conclusion, ‘curl’ is a powerful and versatile tool for Linux users. By understanding ‘curl’ and the protocols it interacts with, you can leverage its full potential and become a more proficient Linux user.

Expanding ‘curl’ Usage: Scripting and Automation

The ‘curl’ command proves its worth beyond simple file downloads. It’s a powerful tool for scripting and automation, particularly in tasks involving network-related operations.

‘curl’ in Scripting

In scripting, ‘curl’ can be used to automate file downloads, API calls, and more. Here’s an example of a bash script that uses ‘curl’ to download a file and then checks if the download was successful:

#!/bin/bash

# Download file
url=https://example.com/file.txt
curl -O $url

# Check if download was successful
if [ $? -eq 0 ]; then
    echo "Download successful."
else
    echo "Download failed."
fi

# Output:
# 'Download successful.'

In this script, ‘curl’ attempts to download a file from the specified URL. The $? variable in bash stores the exit status of the last executed command. If ‘curl’ successfully downloads the file, it returns 0, and the script prints ‘Download successful.’ If not, it prints ‘Download failed.’

‘curl’ in Automation

‘curl’ can also be used in automation. For instance, you could set up a cron job that uses ‘curl’ to download a daily report from a website and then process the report with another script.

Exploring Related Commands and Concepts

‘curl’ is just one of many powerful tools available in the Linux command line. If you’re interested in network-related operations, you might also want to explore the ‘wget’, ‘netcat’, and ‘telnet’ commands. If you’re interested in scripting and automation, you might want to learn more about bash scripting, cron jobs, and other related concepts.

Further Resources for ‘curl’ Command Proficiency

If you want to delve deeper into the ‘curl’ command and related topics, here are some resources that you might find helpful:

1. The ‘curl’ project’s official website: An invaluable resource with detailed documentation, tutorials, and support.

2. GNU ‘wget’ official manual: A comprehensive guide to ‘wget’, a similar command to ‘curl’.

3. Advanced Bash-Scripting Guide: An in-depth guide to bash scripting, which can be used with ‘curl’ for automation tasks.

Remember, mastering a command like ‘curl’ takes time and practice. Don’t be afraid to experiment, make mistakes, and learn from them. Happy curling!

Wrapping Up: Installing ‘curl’ for Efficient Web Interactions

In this comprehensive guide, we’ve journeyed through the world of the ‘curl’ command in Linux, a powerful tool for interacting with servers and transferring data over a network.

We began with the basics, learning how to install ‘curl’ on different Linux distributions and exploring simple usage examples. We then ventured into more advanced territory, demonstrating the installation of ‘curl’ from source and installation of specific versions. We also showcased how to troubleshoot common ‘curl’ issues and how to use ‘curl’ in scripting and automation.

Along the way, we tackled common challenges you might face when using ‘curl’, such as command not found errors, SSL certificate problems, and slow download speeds, providing you with solutions and workarounds for each issue.

We also looked at alternative approaches to downloading files in Linux, comparing ‘curl’ with ‘wget’. Here’s a quick comparison of these tools:

Whether you’re just starting out with ‘curl’ or you’re looking to level up your web interaction skills, we hope this guide has given you a deeper understanding of ‘curl’ and its capabilities.

With its wide range of supported protocols and flexibility, ‘curl’ is a powerful tool for any Linux user. Now, you’re well equipped to handle any web interaction tasks using ‘curl’. Happy curling!