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One of the most valuable benefits of having computers take charge of many aspects of our lives is the way they can complete tasks over and over again, following a defined schedule without complaint. How do they do this? The answer is something called “cron jobs”.

In this post, you’ll learn exactly what a cron job is, why people use them, and how you can use cron jobs yourself for automating mundane tasks on your server.

But even if you’re not a Linux expert then don’t worry, we will also share a novel method for novice Linux users to manage their system much more effectively using cron jobs.

Let’s get started!

What is a Cron Job?

A cron job is a command or a script that is executed by the cron daemon, a background service that runs on Linux systems and which checks for scheduled tasks. A cron job consists of two parts: a schedule and a command.

• The schedule defines when and how often the command should run.
• The command defines what should be executed.

Let’s take a look at each of them individually.

Understanding Cron Schedules

The schedule is specified using a special syntax that consists of five fields:

1. minute
2. hour
3. day of month
4. month
5. day of week.

Each field can have a single value, a range of values, a list of values, or a special character. The fields are separated by spaces or tabs.

Here is an example of a schedule:

30 10 * * 1-5

The above schedule means that the specified command should run at 10:30 AM on every weekday (Monday to Friday). The asterisk (*) means any value, and the dash (-) means a range of values. You can also use a comma (,) to separate multiple values, a slash (/) to specify increments, and predefined keywords, such as @reboot, @daily, @weekly.

You can use these predefined keywords to make your scripts more readable. For example, if you want to run something once a week then instead of writing 0 0 * * 0, you can simply write @weekly.

To learn more about creating cron schedules, we recommend you take a look at these useful articles:

• Cron examples by Crontab.guru
• Common Cron Job Schedules

Understanding Cron Task

The second part of the cron syntax defines a task that needs to be completed. It can be either any valid Linux command, or a path to a script that can be executed. The command can have arguments, redirections, pipes, etc. The output of the command is usually sent to the user’s email, unless it is redirected to a file or another command.

Here is an example of a command:

/usr/bin/backup.sh

This command runs a script that performs a backup operation. The script must have the executable permission, and the correct shebang line.

Why Use Cron Jobs?

Cron jobs are extremely valuable for automating repetitive or periodic tasks, such as backups, updates, notifications, etc. You can use these schedules for a variety of tasks such as:

• Importing data from another system on a recurring basis
• Making changes to properties in your CRM based on time and date (such as annually, monthly, or daily)
• Running system management commands, such as clearing the cache, updating packages, checking disk space, etc.
• Running scripts or programs that perform specific tasks, such as generating reports, sending emails, scraping websites, etc.
• Scheduling backups of your files, databases, or websites
• Many popular web platforms such as Magento and WordPress rely on cron jobs to perform various tasks related to their functionality and performance. Some of these tasks are: indexing databases, sending newsletters, processing orders, etc.

Suggested read: Understanding WordPress Cron Jobs

How to Create a Cron Job

To create a cron job on Linux, you need to edit the crontab file. This is a text file that stores the cron jobs for a particular user account on the computer. You can use the crontab -e command to edit the crontab file using your default editor. If you are running the command for the first time, you may be asked to choose an editor, such as nano, vim, emacs, etc.

Suggested read: How to create WordPress cron jobs with wp-cli tool

Select the number corresponding to your desired editor to use that one, or just press ‘Enter’ to use the default editor.

When working on the crontab file, you should keep following things in mind:

1. Lines starting with the hash (#) sign are comments, and are completely ignored by the computer
2. Blank lines are also ignored
3. All other lines represents an individual cron job

As noted previously, cron jobs follow the schedule command format. If we want to use the schedule and command described above, we will add the following line to the crontab file.

Note that at the end of the command, we have added a helpful comment that will make it easy to identify this cron task if we ever wish to make changes to it in the future.

30 10 * * 1-5 /usr/bin/backup.sh # Run backup.sh at 10:30 AM on weekdays

You can add, modify, or delete lines in the crontab file to create or update your cron jobs. After you save and exit the editor, the cron daemon will reload the crontab file and apply the changes. You can also use the crontab -l command to list the current crontab file, or the crontab -r command to remove the crontab file.

For more details on the cron schedule syntax, you can check the crontab man page.

How to Manage a Cron Job

Cron jobs are usually set and forget – there isn’t much that you usually need to do once it has been enabled. However, if you suspect that your jobs are not running properly, then you can use the following tips to manage and troubleshoot your cron jobs:

• To disable a cron job temporarily, you can comment out the line in the crontab file by adding a hash sign # at the beginning of the line.
• To enable a cron job, you can uncomment the line in the crontab file by removing the hash sign # at the beginning of the line.
• To view the status of the cron daemon, you can use the systemctl command or the service command, depending on your Linux distribution. For example, systemctl status cron or service cron status.

• To restart the cron daemon, you can use the systemctl command or the service command, depending on your Linux distribution. For example, systemctl restart cron or service cron restart.

Creating Cron Jobs the Easy Way with RunCloud

Managing Linux can be hard and difficult, especially for beginners or non-technical users. Linux commands and scripts can be complex and error-prone, and require a lot of knowledge and experience to use them effectively. This is why we built RunCloud!

RunCloud is a cloud server management panel that simplifies and automates the process of creating and managing cron jobs on Linux servers.

We provide a feature-rich GUI that helps you create and edit cron jobs right from the dashboard, without the need to use the terminal or edit the crontab file manually.

To create a new job on your server, simply open your RunCloud dashboard and click on the “Cronjob” tab in the left menu.

On the next screen, just click on “Add New Job” to get started.

When creating a new job, simply fill in the basic information, such as the name of the job and the command that you want to execute – everything else will be pre-filled for you.

The above screenshot shows an example of a cron job created using RunCloud. This cron job will run the WordPress cron events for the app-pat2 web application every minute, using the runcloud user and the wp-cli tool.

Let’s take a look at each of the settings that you can modify.

• Job Label: This is a name or description for the cron job, which can help you identify and organize your cron jobs.
• User: This is the system user that will execute the cron job. You can choose any user that has the permission to run the command or script.
• Vendor Binary: This is the binary or interpreter that will run the command or script. You can choose from a list of vendor binaries provided by RunCloud, such as /bin/bash, /usr/bin/php, etc. or you can write your own binary inside the command field.
• Command: This field contains the actual command or script that will be executed by the cron job. You can write any valid Linux command or a path to a script that can be executed. In this case, the command is using the wp-cli tool to run the WordPress cron events for the app-pat2 web application.
• Run In: This is the schedule or frequency of the cron job. You can choose from a list of predefined settings, such as every minute, every hour, every day, etc., or you can use the custom settings to specify your own schedule using the cron syntax.

Why Use RunCloud?

RunCloud’s cron job feature is more powerful than the traditional way of creating and managing cron jobs on Linux systems, because it offers the following advantages:

• It has a user-friendly and intuitive GUI that makes it easy to create and edit cron jobs, without the need to use the terminal or edit the crontab file manually.
• It provides predefined settings and custom settings for scheduling your cron jobs, which can save you time and avoid errors in writing the cron syntax.
• It provides a list of vendor binaries that you can use to run your commands or scripts, which can simplify your commands and ensure compatibility with your server environment.
• It allows you to choose any system user that has the permission to run the command or script, which can enhance the security and flexibility of your cron jobs.
• It allows you to quickly Activate or Disable individual cron jobs without ever needing to log in to your server.
• It enables you to run cron jobs on demand right from your RunCloud dashboard.

Conclusion

In this article, we have shown you how to create and manage cron jobs on Linux using the crontab command and the cron daemon. Cron jobs are a powerful and convenient way to automate tasks on Linux systems. We hope you have found this article useful and informative. If you have any questions or feedback, please feel free to leave a comment below.

If you are looking for a simple and powerful way to create and manage cron jobs on Linux servers, you should try RunCloud.

RunCloud is a cloud server management panel that simplifies and automates the process of managing Linux servers.

RunCloud is more than just a cron job manager. It is a complete solution for managing your web applications, databases, backups, security, and performance on Linux servers. You can use RunCloud to deploy, configure, and optimize your web applications using any PHP version and web server stack.

RunCloud is compatible with any cloud provider, such as AWS, Google Cloud, DigitalOcean, Linode, Vultr, etc. If you want to experience the power and simplicity of RunCloud, you can sign up for a RunCloud account today!

Are you working on a bash script that needs to be executed without any human inputs? Do your scripts fail when the process of copying files encounters a problem?

If you answered “yes” to either of these questions then you’re in the right place.

In this post, we will take a quick look at the cp command in Linux, and examine how it can be used in different scenarios.

How to Copy Files in Linux CLI

Copying files is one of the simplest actions that you can perform on a computer. To copy files via the command line you can use the cp command, which stands for ‘copy’. The general syntax for the cp command is:

cp [OPTIONS] SOURCE(s)... DESTINATION

The SOURCE(s) can be one or more files or directories, and the DESTINATION can be a single file or directory. If you’ve passed more than two parameters to the command, then the last one is always considered the destination, and all other parameters before it are considered the source(s).

• If the DESTINATION is a directory, the SOURCE files or directories are copied into it.
• If the DESTINATION is a file, the SOURCE file is copied and renamed as the DESTINATION file.

Here is a simple example of how to copy a file named file.txt from the current directory to another directory named backup:

cp file.txt backup/

This will copy the file file.txt to the backup directory with the same name. If you want to copy the file with a different name, you can specify the new name after the backup directory:

cp file.txt backup/new_file.txt

This will copy the file file.txt to the backup directory as new_file.txt.

How to Overwrite Existing Files

By default, cp will overwrite any existing files in the destination without asking for confirmation. However, this behavior can be changed by using different flags or options with the cp command. Here are some of the common flags that can affect how cp handles overwriting:

• -f or --force: This option will force cp to overwrite any existing files in the destination, even if they cannot be opened or removed. This option will also ignore any -n option that is used before it.
  
  For example, cp -f source.txt destination.txt will overwrite destination.txt with source.txt, regardless of any permissions or errors.
• -i or --interactive: This option will make cp prompt the user before overwriting any existing files in the destination. You can choose to overwrite or skip the file by typing y or n and then pressing Enter.
  
  If you’re copying multiple files at once, you will be prompted for each file separately. If you don’t type anything and press Enter then the file will not be overwritten.
  
  This option will also override any -n option that is used before it. For example, cp -i source.txt destination.txt will ask the user if they want to overwrite destination.txt with source.txt, and proceed accordingly.
• -n or --no-clobber: This option will prevent cp from overwriting any existing files in the destination. If the destination file already exists, cp will skip it and move on to the next file. This option will also override any -i option that is used before it.
  
  For example, cp -n source.txt destination.txt will not overwrite destination.txt with source.txt, if destination.txt already exists.
• -u or --update: This option will make cp copy only when the source file is newer than the destination file, or when the destination file does not exist. This can be useful for updating or synchronizing files between different locations.
  
  For example, cp -u source.txt destination.txt will overwrite destination.txt with source.txt, only if source.txt is newer or destination.txt does not exist.

Note that these flags can be combined to achieve different effects. For example, cp -uf source.txt destination.txt will force cp to overwrite destination.txt with source.txt, only if source.txt is newer or destination.txt does not exist.

Changing the Default Behavior

On some computers, the default behavior of the cp command can be affected by an alias. An alias is a way of creating a shortcut or a new name for a command, with some predefined options.

For example, some Linux distributions come with the following alias pre-defined in their code:

alias cp='cp -i'

This means that whenever the user types cp, the shell will actually run cp -i, which will prompt the user before overwriting any files.

Checking For An Existing Alias

If you’re not sure whether your computer has a predefined alias, then you can run the following command to list all aliases, and then look to see whether the cp is present in the output:

alias

Removing An Alias

To remove the alias for cp, you can run the command unalias cp, which will restore the default behavior of cp.

In the above example, we can see that an alias was defined for the cp command. After executing the unalias command, the alias entry was removed from the list.

Temporarily Bypass An Alias

If you don’t want to permanently remove the alias, you have an option to use a backslash before the cp command to bypass the alias and run the original command. For example, \cp source.txt destination.txt will overwrite destination.txt with source.txt, without prompting the user.

In the above example, we can see that the user was prompted for input when executing the copy operation, but not when the command was prefixed with the \ character.

Automatically Accepting All Prompts

In Linux there are multiple ways to do the same thing using different methods. If you don’t want to use the in-built -f option to overwrite files then you can use the copy command in conjunction with the yes command to automatically respond with y to all prompts.

yes | cp -v source destination

In the above example, we can see that the copy command prompted us for input before replacing each file, but the yes command responded ‘yes’ to each and every single one of them nearly instantaneously.

Wrapping Up

In this article, we have discussed how to copy files and directories in Linux via the command line. We have also explained different options and features of the copy command that are helpful in day-to-day usage.

If you’re learning Linux to better manage your servers, we wish you all the best! However, you don’t need to be a Linux expert to host websites on the internet. RunCloud makes it extremely easy to deploy and manage websites using a user-friendly dashboard, and provides complete freedom to tinker under the hood.

Whether you’re a beginner or a seasoned professional with decades of experience, sooner or later everyone makes a configuration change that completely renders websites useless. RunCloud has idiot-proofed many complex operations such as updating server configurations, installing SSL certificates, deleting applications, etc. – all of which makes it difficult for novice users to crash their website, and provides an extra set of guide-rails to advanced users.

RunCloud is a versatile and reliable tool that can help you manage your server on your own, without the hassle and cost of hiring a system administrator. Don’t miss this opportunity to take your server management to the next level. Sign up for RunCloud today and enjoy the benefits of a cloud-based server management platform that is fast, secure, and easy to use.

Are you using Linux to manage your servers?

Do you find yourself frequently copying the output on the terminal and pasting it into different bash commands?

If you answered “Yes”, then you should definitely start using the Pipes and xargs command in Linux.

These are extremely helpful Linux utilities that will save you time and effort when working with the command line. Using these opens up so many possibilities for manipulating and processing data in the command line.

If you want to perform complex actions in the Linux terminal and grow your Linux skills past the basic level, you will definitely need to learn how to use these commands.

In this article, you will learn exactly what xargs is, how it is different from pipes, and when to use which tool.

Let’s get started!

What Are Pipes in Linux?

Pipes are a way of connecting the standard output of one command to the standard input of another command in Linux. This allows you to chain commands together and process data in a stream.

To understand pipes, imagine two people talking on a ‘tin can telephone’. Here the first person is passing some information and the second person can only hear the information being passed. In this example, the telephone is acting as a pipe and the second person cannot jump to the end of the conversation without listening to the entire conversation first.

Similarly, pipes allow you to pass along information between processes and help you manipulate and process data in various ways. The syntax of pipes in pretty simple, just put a | sign between two commands.

first | second

In the above example, the output of the first will be used as the input for the second. This is pretty useful when working in the CLI.

For example, if you want to count the number of files and directories in the current directory, you can use a pipe like this:

ls | wc -l

This command will list all files and directories in the current directory, and then pipe the output to the wc command, which will count the number of lines. The pipe character | is used to redirect the output of command to the other. The command on the left side of the pipe sends its output to the command on the right side of the pipe, which receives it as its input.

Pipes are useful for performing operations on multiple items of data without having to write a loop or a script. You can also use multiple pipes to create a pipeline of commands, such as:

find . -name "*.txt" | grep "hello" | wc -l

The above command will find all files in the current directory and its subdirectories that have the “.txt” extension, and then pass them to the grep command, which will filter only the files that contain the word “hello”. The output of the grep command will then be piped to the wc command, which will count the number of lines. The result of this command is the number of files that have the “.txt” extension and the word “hello” in them.

What is the xargs Command?

The xargs utility in Linux reads data from standard input and converts it into command line arguments for another command. This allows you to perform operations on large amounts of data without having to write a loop or a script.

For most part, this is pretty similar to the pipe operator that we discussed above, but with one major difference. The pipe operator redirects its output to the standard input of the second command, whereas the xargs utility will create a list of all the data and then pass it as command line arguments to the second command.

To understand this, imagine the same person from above writing the information on a piece of paper and then passing it along to the second person. In this example, the paper is the xargs utility and the second person can see all the information at once.

Having the ability to pass along information via the command line arguments opens up many possibilities. For example, if you want to delete all files that have the word “temp” in their name, you can use xargs like this:

find . -name "*temp*" | xargs rm

This command will find all files in the current directory and its subdirectories that have “temp” in their name, and then pass them as arguments to the rm command, which will delete them.

Xargs or Pipes: Which One to Use?

You may have already spotted that these two commands are basically the same apart from one key detail – pipes are useful for processing data in a stream.

The main difference between pipes and xargs is that pipes pass data as standard input, while xargs passes data as command line arguments.

This means that pipes will only work with commands that accept standard input, while xargs can only work with commands that accept command line arguments.

What Are Standard Input and Command Line Arguments?

Standard input and command line arguments are two different ways of passing data to a program in Linux.

• Standard input is a stream of data that the program reads from its standard input file descriptor, usually the keyboard or a pipe.
• Command line arguments are strings of text that the program receives as parameters when it is invoked from the shell.

For example, if you run the command ls -l /home, the program ls will receive two command line arguments: -l and /home. The program can access these arguments using the argc and argv variables in C, or equivalent mechanisms in other languages.

Although many software tools accept both command line arguments and standard input, not all do. As a software user, we often do not have the option to change how the program processes input.

For example, the command echo will print whatever you type after it, but it will not read from standard input. If you try to pipe the output of ls to echo, you will get nothing:

ls | echo

This is where xargs comes in handy – xargs will take the data from standard input and convert it into arguments for the command you specify. For example, if you want to print the names of all files and directories in the current directory, you can use xargs with echo like this:

ls | xargs echo

This command will list all files and directories in the current directory, and then pass them as arguments to the echo command, which will print them.

The choice of using pipes or xargs depends on the situation and the commands you want to use. In general, pipes are more efficient and elegant, as they avoid creating intermediate files or processes.

However, xargs can be more flexible and powerful, as it allows you to customize the arguments and options for the command you want to execute. It also has many options that allow you to handle different scenarios, such as limiting the number of arguments, replacing placeholders, prompting the user, or dealing with filenames that contain spaces or special characters. Let’s see some of these use cases in the next section.

How to Use xargs like a Pro in Linux

xargs has many options that allow you to customize its behavior and handle different situations. Here are some of the most common and useful ones:

Limit the Number of Arguments

The -n option specifies the maximum number of arguments to pass to each invocation of the command. For example, if you want to print the names of all files and directories in the current directory in groups of three, you can use xargs with -n 3 like this:

ls | xargs -n 3 echo

This command will list all files and directories in the current directory, and then pass them as arguments to the echo command in groups of three. Then the echo command will be executed multiple times, once for each group of three arguments that it received.

Replace Placeholder Text

When working in the command line, you will often encounter cases where you need to run many simple commands, each with a tiny change. The -I option allows you to specify a placeholder that will be replaced by each argument in the command.

For example, if you want to create many files in your server which follow a common pattern, then you can use xargs with -I {} like this:

seq 12 | xargs -I {} touch runcloud_{}.txt

The above command will create a sequence of twelve numbers, then use those numbers to create twelve files that follow the pattern runcloud_#.txt.

Prompt User For Confirmation

When generating commands on the fly, it is pretty easy to do irreversible damage to your server. The smart way to use xargs is by letting it generate all the commands and then manually confirming it before it can be executed.

To do this, use the -p flag which prompts the user before executing each command and waits for confirmation. For example, if you want to delete all files that start with the word “runcloud”, but you want to confirm each deletion in batches of four, you can use xargs with -p like this:

find . -name "runcloud*" | xargs -p -n 4 rm

This command will find all files in the current directory and its subdirectories that have “runcloud” in their name, and then pass them as arguments to the rm command, which will prompt the user before deleting each file and wait for a “yes” or “no” answer.

In the above example, we can see that first we created twelve files. Then we used the find function to find any files that match our criteria and then passed them along in batches of four. The resulting rm command is displayed in the terminal and we can press y or n to confirm or reject the action.

After the command has been executed, we can see that the files in the second batch of deletion remain untouched because we pressed n when we were asked to confirm the deletion, whereas all the other files that matched the criteria were removed.

Process Files with Weird Names

The xargs utility is not secure, because it can execute arbitrary commands if the input contains malicious or unexpected data. For example, if the input contains spaces, quotes, or other special characters, xargs may interpret them as part of the command or the arguments, and cause unwanted or harmful effects.

If you’re working with data that contains spaces, special characters, or even foreign language text, then it is always a good idea to terminate the output of a line using null characters to avoid unexpected output.

The -0 or –null flag expects the input to be null-terminated, meaning that each argument is separated by a null character instead of a space or a newline. For example, if you want to delete all files that have the word “temp” in their name, but some of them have spaces in their name, you can use xargs with -0 like this:

find . -name "runcloud*" -print0 | xargs -0 rm

This command will find all files in the current directory and its subdirectories that start with “runcloud” and then print them with a null character after each name. xargs will then read the input as null-terminated and pass them as arguments to the rm command, which will delete them.

In the above example, we can see that terminating the output with a null character allows the program to gracefully execute the given command. If we had omitted the null termination step, we would have encountered different errors.

After Action Report

Both pipe and xargs are powerful and versatile utilities that can help you perform different operations on data in the command line. There is a character limit to xargs, but it depends on the system and the options used.

By default, it tries to pass as many arguments as possible to the command, without exceeding the maximum length of the command line. To see the limits of xargs on your system, you can use the --show-limits option.

Normally, xargs runs the second command once, even if there is no input (output from the first command). This option is useful to avoid errors or unwanted actions when the input is empty. To suppress this, you can specify --no-run-if-empty option.

These are just some of the options that xargs offers. You can find more information and examples by typing man xargs or xargs --help in the command line.

It is clear that xargs is a must-learn tool for any Linux user who wants to go beyond the basics and explore the possibilities of the command line.

However, if you don’t want to become a master in Linux command line utilities, but still want to manage your Linux server yourself, then you should check out RunCloud.

RunCloud is a cloud-based server management platform that lets you deploy, configure, and monitor your web applications with ease. If you’re an advanced user, you can take advantage of the CLI and API, as RunCloud gives you full control over your server.

If you’re not comfortable with using the CLI or the API, don’t worry. RunCloud also offers an easy to navigate dashboard that can deploy applications in a breeze. You can also use RunCloud to set up SSL certificates, domains, cron jobs, firewalls, and more.

RunCloud is a versatile and reliable tool that can help you manage your server on your own, without the hassle and cost of hiring a system administrator. Don’t miss this opportunity to take your server management to the next level. Sign up for RunCloud today and enjoy the benefits of a cloud-based server management platform that is fast, secure, and easy to use.