Category Archives: bash if directory exists

Bash if directory exists

By | 13.07.2020

While creating a bash script, it is commonly helpful to test if file exists before attempting to perform some action with it. This is a job for the test command, that allows to check if file exists and what type is it.

Cool Tip: Create a clever bash script! Make it do more tests! Check easily whether a string exists in a file! In the examples below, lets print corresponding messages depending on the results of the test command. Lets create a bash script, that will check whether a passed as an argument file exists or not, by printing a corresponding message.

Cool Tip: A good bash script prints usage and exits if arguments are not provided! It is very simple to configure! In the examples above with the -f operator we only check whether a file exists and it is a regular file.

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bash if directory exists

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Home Questions Tags Users Unanswered. How to check if a directory exists in Linux command line? Ask Question. Asked 10 years, 3 months ago. Active 3 years, 3 months ago. Viewed 82k times. Emanuel Emanuel. So mark it as the solution. Active Oldest Votes. Stefano Borini Stefano Borini 2, 5 5 gold badges 29 29 silver badges 48 48 bronze badges.

I need it in command line, not in a script. That is command line. Not everybody's shell is bash!

bash if directory exists

Stefano Borini: I still use tcsh because I'm too lazy to rewrite my. But more to the point: this might have explained the OP's problem. Brian Showalter Brian Showalter 1 1 silver badge 4 4 bronze badges. Then figure out what your shell is. Perhaps csh or tcsh? The canonical way is to use the test 1 utility: test -d path where "path" is the pathname of the directory in question. Steve Emmerson Steve Emmerson 2 2 silver badges 7 7 bronze badges. The command doesn't appear to be doing by itself but when joined with a echo "Directory Exists".

Ejaz 1 1 gold badge 3 3 silver badges 18 18 bronze badges. Between "[" and "-" MUST be a space. This should work on Bourne and Bash shell. Marcelo Filho 4 4 bronze badges. Welcome to Super User! This duplicates another answer and adds no new content.

Please don't post an answer unless you actually have something new to contribute. Sign up or log in Sign up using Google.If you use bash for scripting you will undoubtedly have to use conditions a lot, for example for an if … then construct or a while loop. The syntax of these conditions can seem a bit daunting to learn and use. This tutorial aims to help the reader understanding conditions in bash, and provides a comprehensive list of the possibilities.

A small amount of general shell knowledge is assumed. Difficulty: Basic — Medium. Bash features a lot of built-in checks and comparisons, coming in quite handy in many situations.

The condition in this example is essentially a command. It may sound strange, but surrounding a comparison with square brackets is the same as using the built-in test command, like this:. There also are built-in checks that are more specific to shells.

What about this one? This way, you can make sure a usable file exists before doing something with it. You can even check if a file is readable! The condition is, depending on its type, surrounded by certain brackets, eg. You can read about the different types further on in the tutorial.

You can add commands to be executed when the condition is false using the else keyword, and use the elif elseif keyword to execute commands on another condition if the primary condition is false.

The else keyword always comes last. If so, we read it into a variable. The condition at elif is only executed if the condition at if was false. The commands belonging to else are only executed if both conditions are false. When you start writing and using your own conditions, there are some rules you should know to prevent getting errors that are hard to trace. Here follow three important ones:. The words ifthenelseelif and fi are shell keywords, meaning that they cannot share the same line.

By quoting I mean:. There are a few cases in which you should not quote, but they are rare. You will see one of them further on in the tutorial. Also, there are two things that may be useful to know:.

You can combine conditions by using certain operators. You can read more about these combining expressions at the respective condition syntaxes. It is outside the scope of this tutorial to explain those, but you can read about them at the Bash Guide for Beginners. There are more syntaxes, however, as you will read in the next section. It supports three types of conditions:.

For more file-based conditions see the table below. String-based conditions Allows checks on a string and comparing of strings.

Example two:.

Bash: Test If File Exists

For more string-based conditions see the table below. Arithmetic number-based conditions Allows comparing integer numbers. For more arithmetic conditions see the table below.

Double-bracket syntax You may have encountered conditions enclosed in double square brackets already, which look like this:.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. It only takes a minute to sign up.

Here is a single command which will recursively list symlinks whose target is a directory starting in the current directory :. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. How do I check if a file is a symbolic link to a directory? Ask Question.

Asked 6 years, 6 months ago. Active 3 years, 8 months ago. Viewed k times. Gilles 'SO- stop being evil' k gold badges silver badges bronze badges. Active Oldest Votes. Something with portability between shells iirc. Lennart OP's example code uses [[and I took that as the logical starting point. A discussion of the merits of [ vs [[ is out of scope for this answer but available here.

Here is a single command which will recursively list symlinks whose target is a directory starting in the current directory : find.

Mark Edington Mark Edington 3 3 silver badges 9 9 bronze badges. Using find and a while read for that is kinda overkill Sign up or log in Sign up using Google. Sign up using Facebook.Welcome to the most active Linux Forum on the web. Welcome to LinuxQuestions. You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features.

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Introduction to Linux - A Hands on Guide This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter. For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration.

This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. They hope these examples will help you to get a better understanding of the Linux system and that you feel encouraged to try out things on your own. Click Here to receive this Complete Guide absolutely free. I am running this in a crontab file and I dont want any output telling me that the directory exists.

I just want to check if the directory doesnt exist, create one else do nothing not even a message telling me that the directory exists. Here is what I tried: 1.

Any suggestions?

bash if directory exists

Try using double brackets: Code:. Your third try is the proper syntax. Try quoting your variable Code:. Last edited by sploot; at AM. Reason: fixed it. Use mkdir -p instead.

It does not complain if directory already exists.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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However, as Jon Ericson points out, subsequent commands may not work as intended if you do not take into account that a symbolic link to a directory will also pass this check. Take particular note of the double-quotes used to wrap the variables, the reason for this is explained by 8jean in another answer. If the variables contain spaces or other unusual characters it will probably cause the script to fail. Remember to always wrap variables in double quotes when referencing them in a bash script.

Kids these days grow up with the idea that they can have spaces and lots of other funny characters in their directory names. Back in my days, we didn't have no fancy spaces!

You don't want that. So use this. File under: "When is a directory not a directory? You can find more information in the Bash manual on Bash conditional expressions and the [ builtin command and the [[ compound commmand. I find the double-bracket version of test makes writing logic tests more natural:.

Note : Be careful, leave empty spaces on either side of both opening and closing braces. Note: The test command is same as conditional expression [ see: man [so it's portable across shell scripts. It will also give more information than I will be able to provide. By performing the cd inside a subshell If the directory exists, this subshell and the function are just a no-op.

This is a more elaborate form of parameter substitution which is explained in more detail below. Tl;dr: If the string passed into this function is empty, we again exit from the subshell If parameter is set and is non-null then substitute its value; otherwise, print word and exit from the shell if not interactive. If word is omitted then a standard message is printed.

If the colon : is omitted from the above expressions, then the shell only checks whether parameter is set or not. The phrasing here is peculiar to the shell documentation, as word may refer to any reasonable string, including whitespace. In this particular case, I know that the standard error message 1: parameter not set is not sufficient, so I zoom in on the type of value that we expect here - the pathname of a directory.

A philosphical note: The shell is not an object oriented language, so the message says pathnamenot directory. At this level, I'd rather keep it simple - the arguments to a function are just strings. Both combinations. In the following example, it checks the existence of the folder in the current directory:.

Conditions in bash scripting (if statements)

Note that [[]] is not as portable as []but since most people work with modern versions of Bash since after all, most people don't even work with command line :-pthe benefit is greater than the trouble. Have you considered just doing whatever you want to do in the if rather than looking before you leap? IE, if you want to check for the existence of a directory before you enter it, try just doing this:.

If the path you give to pushd exists, you'll enter it and it'll exit with 0which means the then portion of the statement will execute. If it doesn't exist, nothing will happen other than some output saying the directory doesn't exist, which is probably a helpful side-effect anyways for debugging. Same thing works with cdmvrmetc If you try them on files that do exist, the command will execute and exit with a status of 0allowing your then block to execute.

If you want to create the directory and it does not exist yet, then the simplest technique is to use mkdir -p which creates the directory — and any missing directories up the path — and does not fail if the directory already exists, so you can do it all at once with:.

This is not completely trueThere are several functions in Linux that only work if a particular file or directory exists. Bash is a shell that interprets commands. You can use a bash command to check if a file or directory exists.

Note: You may encounter the term bash script. This is a sequence of several commands to the shell. A script can be saved as a file and is often used to automate multiple system commands into a single action. The first line executes the test to see if the file exists. The second command, echodisplays the results 0 meaning that the file exists, 1 means no file was found. To c heck if a directory exists, s witch out the —f option on the test command for —d for directory :. This command works the same as it does for files, so using brackets instead of the test command works here also.

Note: If you are searching for a file or directory because you need to delete it, refer to our guide on removing files and directories with Linux command line.

Typically, testing for a file returns 0 true if the file exists, and 1 false if the file does not exist. For some operations, you may want to reverse the logic. The exclamation point! This command makes sure there is not a file named test. You should see test. You can use a similar command for a directory — replace the —f option with —d :.

As usual, changing the —f option to —d lets you run the same test for multiple directories. The previous commands work well for a simple two-line command at a command prompt. You can also use bash with multiple commands. When several commands are strung together, they are called a script. A script is usually saved as a file and executed. Scripting also uses logical operators to test for a condition, then takes action based on the results of the test. Enter one of the snippets from below, including the!

Use Ctrl-o to save the file, then Ctrl-x to exit Nano. Then, run the script by entering:. The following code snippet tests for the presence of a particular file. If the file exists, the script displays File exists on the screen. Just replace the —f option with —d :. If it exists, the system displays File exists. There are many other options available.

Please consult the main page test ——help for additional options. You can now use bash to check if a file and directory exist. You can also create simple test scripts as you now understand the functions of a basic bash script file. Screen is a powerful tool for working in the command line. It lets you create, monitor, and switch between…. Read More.

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