However, Bash does not contain any built-in function to combine string data or variables. So there are lots of useful solutions to the question - but which is fastest / uses the fewest resources? I need help with some code to work out if a variable (string) contains any integers. Also, you need spaces between [[, the elements of the comparison, and ]].Spaces are critical delimiters in the shell; do not leave them out. A string can be any sequence of characters. The -z operator functions similarly like -n operator. The easiest method to perform string concatenation in bash is to write variables side by side. The output of the following line of code will be forward 2. https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/229585#229585, This is probably the best solution since it is portable to posix shells. To do so, just add '-not' parameter in the find command as shown below. @bukzor Quotes stopped working here as of Bash 3.2+: Note that the order in which the test occurs matters. Strangely one of the easiest and most portable ways to check for "not contains" in sh is to use the case statement. That is to say, if you're writing a bash script where two or more tests will have to return "True", then you have to use &&. This will throw error code 1 since the string is completely substituted (due to *). Also note that this will be much much slower than using a case statement. The old rule about using external utilities without need holds true. <<< makes the shell expand the next word and use it as the input to the command, a one-line version of the << here document (I'm not sure whether this is standard or a Bashism). Leave a space between the brackets and the contents. For that reason I'd use grep, and not the [ command. Bash conditional statements include the if statement, else, elif, etc. Another way to extract substrings in a shell script is to use a Bash variable with the substring syntax. Wildcards (like *.out) aren't expanded inside double-quotes or on the right side of an assignment, so yours never gets converted to a list of files (until you echo it without double-quotes). +1. You may not have experienced it, but it does happen. Below is an example: Most importantly, you should add spaces around the square brackets. It is written in Bash. To check if two strings are not equal in bash scripting, use bash if statement and not equal to!= operator. I need an if statement for a Linux bash shell script, to determine if a string contains one or more of a given set of characters. Imparting the underlying logic is more important than just giving the code, because it helps the OP and other readers fix this and similar issues themselves, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/11281580#11281580, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/54490453#54490453, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/59179141#59179141, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/40530610#40530610, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/3587443#3587443, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/60884380#60884380, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/49765399#49765399. However, when a variable is defined but has no value, then the variable is “Not Set.” Similarly, when a variable is defined and has a value, then it is “Set.” Thus, declared variable but no value equals to “Not Set,” and declared variable with value equals to “Set.”. It returns no error. How to add a prefix string at the beginning of each line in Bash shell script on Linux? DiskInternals Linux Reader is a handy freeware program that lets you view files saved on Ext2/3/4 partitions or any Linux-compatible partition while … This is another example to read a file line by line and check if a string contains a specific substring and do some operation on it. -z is the second supported bash string comparison operator used to check if a string is empty or not. Conditional Expression Meaning-a file: True if file exists.-b file: True if file exists and is a block special file.-c file: True if file exists and is a character special file.-d file: True if file exists and is a directory.-e file: True if file exists.-f file: True if file exists and is a regular file.-g file: True if file exists and its set-group-id bit is set.-h file Work in busybox. Piping out to 100000 greps is predictably painful! no bashisms), @technosaurus I find it rather odd to criticize "bashism" in a question that has only bash tag :), @P.P. There are many ways to test if a string is a substring in bash. Also need to be able to | The UNIX and Linux Forums -n is one of the supported bash string comparison operators used for checking null strings in a bash script. It's not so much a criticism as the preference of a more universal solution over a more limited one. Find And Delete Files That "does not" contain specific text in their names in Linux. Only sh is installed. All rights reserved 2021 - DiskInternals, ltd. How to Access Linux Ext2 or Ext3 on Windows, An Algorithm: How to Create Bash While Loop, Linux Shell: What You Need to Know at First, 5 Basic Shell Script Examples for Your First Script, Bash: How to Check if the File Does Not Exist, How to use bash get script directory in Linux, Bash: How to Loop Through Files in Directory, A Bash‌ ‌Status‌ ‌of‌ Last‌ ‌Command‌, If you want to run shell script in background, The disk you inserted was not readable by this computer error, Bash: How to Check if String Not Empty in Linux. https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/52671757#52671757, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/27726913#27726913, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/527231#527231. Very good! This is quite a crucial action for most advanced users. FREE DOWNLOADVer 4.7, Win ==), not the regex operator =~. fi` is useful when using BusyBox's shell, the inequality of difference. If statement can accept options to perform a specific task. I found to need this functionality quite frequently, so I'm using a home-made shell function in my .bashrc like this which allows me to reuse it as often as I need to, with an easy to remember name: To test if $string1 (say, abc) is contained in $string2 (say, 123abcABC) I just need to run stringinstring "$string1" "$string2" and check for the return value, for example. You can always find out if a string/word/variable contains another string/word in Linux or Unix shell scripting. What I want to do is strip off an individual HTML-tag from the end. The generic needle haystack example is following with variables, This will find any occurance of a or b or c, 2021 Stack Exchange, Inc. user contributions under cc by-sa. In this post we will look at some useful and commmonly used string manipulation technques that should come in handy in … One bug, though: It does not work if the haystack string is empty. This Stack Overflow answer was the only one to trap space and dash characters: My .bash_profile file and how I used grep: If the PATH environment variable includes my two bin directories, don't append them, Original source: http://unstableme.blogspot.com/2008/06/bash-search-letter-in-string-awk.html, Use sed to remove instance of substring from string, If new string differs from old string, substring exists. Now we will run the below-mentioned command to check whether the string is null or not. This script will print the first argument because it is not empty. Both of those are just commands that return an exit status indicating success or failure (just like every other command). The correct version would be. https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/240181#240181, The cost of this is very expensive: doing, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/229993#229993, ephemient's solution above: > ` if [ "$string" != "${string/foo/}" ]; then echo "It's there!" So the simple substitution option predictably wins whether in an extended test or a case. I do use, There was a time when all you had was the original Bourne shell. -n is one of the supported bash string comparison operators used for checking null strings in a bash script. Note: In a tight loop this code will be much slower than using internal Bash shell features, as one (or two) separate processes will be created and connected via pipes. On the other hand, if the string is empty, it won’t return true. How do I find all files that contain string A but do NOT contain string B on linux using bash?. I wrote this same solution myself (because my interpreter wouldn't take the top answers) then went looking for a better one, but found this! It has support for German umlauts. In my last article I shared some examples to get script execution time from within the script.I will continue with articles on shell scripts. Please consider that, years later, people (like me) will stop by to look for this answer and may be pleased to find one that's useful in a wider scope than the original question. ", https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/20460402#20460402. arcshell.io will get you there. Where ?? When -n operator is used, it returns true for every case, but that’s if the string contains characters. But simple style and also POSIX Compliant. Here, we have provided every detail on how to check for empty variables in a bash script, as well as introduce a handy freeware for managing Linux partitions on Windows PC. Example – if -z (to check if string has zero length) The case is portable. Do I use echo and grep? What does basic bash scripting contain? Check if Two Strings are Equal # In most cases, when comparing strings you would want to check whether the strings are equal or not. G'day guys, first post so be gentle. upvote. I suppose this style is a bit more classic -- less dependent upon features of Bash shell. It lacked some commonly required features, so tools like, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/41647131#41647131. Well, you shouldn’t stress yourself that much any longer. Instinctively you think that this "language" requires you to follow an if with a [or a [[.Both of those are just commands that return an exit status indicating success or failure (just like every other command). https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/18441709#18441709, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/29928695#29928695. find . The need to compare strings in a Bash script is relatively common and can be used to check for certain conditions before proceeding on to the next part of a script. The pattern must be: "beginning-of-string, followed by zero-or-more occurrences of, say, :alnum:, followed by end-of-string." This would be even better, if you can figure out some way to put that to a function. The original question asked about “strings” but the tools we’ll be using support regular expressions so we will essentially be answering:. The "str_escape_special_characters" function. How to judge whether its STDERR is redirected to a file in a Bash script on Linux? However, there’s no built-in function for checking empty variables in bash scripts, but bash supports a feature that can help out. The syntax for the simplest form is:Here, 1. When -n operator is used, it returns true for every case, but that’s if the string contains characters. The condition in the if statement often involves a numerical or string test comparison, but it can also be any command that returns a status of 0 when it succeeds and some nonzero status when it fails. The -q option makes grep not output anything, as we only want the return code. As our string StdName has now a value Aqsa Yasin, and the -z string operator knows that the string is not null, so it executes the else part. Bash scripting entails quite a lot of things: writing conditional statements, understanding the various concepts of bash, built-in commands, and how to indicate if a script executed successfully or not. Had to replace an egrep regex in a bash script, this worked perfectly! My recent installation of PCBSD has only csh installed by default. You don't need to quote variables inside [[ ]]. You could just as easily return 1 or 0 instead. Thanks for the answer! For example, check all the users in /etc/passwd having shell /bin/bash. Also note that a simple comparison operator is used (i.e. Bash does not segregate variables by “type”, variables are treated as integer or string depending on the context. If you’re working in Windows and need to access your Linux files on your dual-boot PC, DiskInternals Linux Reader is the best software to use. also extend it a bit further by matching against a list of patterns: https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/384516#384516, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/35780975#35780975, Please add some explanation. It passes the tests shown below. Bash Strings Equal. The syntax looks like this: string=YOUR-STRING echo ${string:P} echo ${string:P:L} Here P is a number that indicates the starting index of the substring and L is the length of the substring. I love it. – Gordon Davisson May 13 '18 at 23:14 In this article, we are going to check and see if a bash string ends with a specific word or string. (a.k.a. Also note that you can reverse the comparison by just switching to != in the test. This issue has been a problem for most dual-boot users. You know how to delete a file that contains a specific phrase in its name. A variable is either defined or not defined. When creating complex or multi-conditional tests, that's when to use these Boolean operators. However, the output would be “First argument is empty” if nothing is contained in the argument. Pretty weird thought! Example 1, check for 'yes' in string (case insensitive): Example 2, check for 'yes' in string (case insensitive): Example 3, check for 'yes' in string (case sensitive): Example 4, check for 'yes' in string (case sensitive): Example 6, exact match (case insensitive): Example 8, wildcard match .ext (case insensitive): As Paul mentioned in his performance comparison: This is POSIX compliant like the 'case "$string" in' the answer provided by Marcus, but it is slightly easier to read than the case statement answer. The accepted answer is best, but since there's more than one way to do it, here's another solution: ${var/search/replace} is $var with the first instance of search replaced by replace, if it is found (it doesn't change $var). If you try to replace foo by nothing, and the string has changed, then obviously foo was found. For me I changed order stringContain() { [ -z "${1##*$2*}" ] && [ -z "$2" -o -n "$1" ]; }; "Search where" "Find what". Wildcard is a symbol used to represent zero, one or more characters. How can I test if it contains another string? Always quote in Bash, IMO. Example – Strings Equal Scenario. To check if two strings are equal in bash scripting, use bash if statement and double equal to == operator. How do you tell if a string contains another string in POSIX sh? Many functions are available: -base64Decode, -base64Encode, -capitalize, -center, -charAt, -concat, -contains, -count, -endsWith, -equals, -equalsIgnoreCase, -reverse, -hashCode, -indexOf, -isAlnum, -isAlpha, -isAscii, -isDigit, -isEmpty, -isHexDigit, -isLowerCase, -isSpace, -isPrintable, -isUpperCase, -isVisible, -lastIndexOf, -length, -matches, -replaceAll, -replaceFirst, -startsWith, -substring, -swapCase, -toLowerCase, -toString, -toUpperCase, -trim, and -zfill. They hope these examples will help you to get a better understanding of the Linux system and … How to escape special characters in a Bash string in Linux? Some may have to shut down or reboot to Linux before accessing their files in EXT4,3,2, XFS and ZFS partitions. How do I find all files that match pattern A but don’t match pattern B?. The easiest approach is to surround the substring with asterisk wildcard symbols (asterisk) * and compare it with the string. Sometimes, a bash script may contain empty variables. This will work just as well: [[ $string ==, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/231298#231298. You need to pass the -z or -n option to the test command or to the if command or use conditional expression.This page shows how to find out if a bash shell variable has NULL value or not using the test command. Many-a-times, AIX installations do not have bash/ksh/whatever by default. So the output will be Hy Aqsa Yasin in the terminal as shown in the below image. I am not sure about using an if statement, but you can get a similar effect with a case statement: As these Stack Overflow answers tell mostly about Bash, I've posted a case independent Bash function at the very bottom of this post... As there are already a lot of answers using Bash-specific features, there is a way working under poorer-featured shells, like BusyBox: This was tested under Bash, Dash, KornShell (ksh) and ash (BusyBox), and the result is always: As asked by @EeroAaltonen here is a version of the same demo, tested under the same shells: Notice: you have to escape or double enclose quotes and/or double quotes: This was tested under BusyBox, Dash, and, of course Bash: ... Or if the submitted string could be empty, as pointed out by @Sjlver, the function would become: or as suggested by Adrian Günter's comment, avoiding -o switches: And inverting the tests to make them potentially quicker: For testing strings without care of case, simply convert each string to lower case: You should remember that shell scripting is less of a language and more of a collection of commands. DiskInternals Linux Reader comes with a succinct interface and works straightforwardly without any algorithm. Compare Strings in Bash. This is the same answer as https://stackoverflow.com/a/229585/11267590. As they say in the Open Source world: "choice is good! @EeroAaltonen How do you find my (new added) function? There are a few ways to find out if a string contains a substring using bash.Below are a couple of ways this can be done without invoking any other processes. Let us now see how to find and delete files that doesn't have a specific phrase or string in their names. You can use Marcus's answer (* wildcards) outside a case statement, too, if you use double brackets: Note that spaces in the needle string need to be placed between double quotes, and the * wildcards should be outside. : This solution works with special characters: Since the POSIX/BusyBox question is closed without providing the right answer (IMHO), I'll post an answer here. The program is available for free, and it supports quite a couple of handy features. 2. The original string will look like: some textmore textzero-or-more-chars The last tag and zero or more chars part should be deleted ONLY if the zero-or-more-chars does NOT contain any of the following: a-z A-Z 0-9,.: It is a conditional statement that allows a test before performing another statement. Hi, if empty strings are false, why do you consider it clumsy? is my unknown operator. Many non-Linux nixes have only sh (which may or may not be some variant of ksh on solaris, others, I dunno). As Paul pointed out, don't use it in a loop. It is best to put these to use when the logic does not get overly complicated. In Bash script, how to join multiple lines from a file? @nicodjimenez you can not target exit status any more with this solution. -name "*" | xargs grep "myfunc" 2> /dev/null, This is wonderful because it's so compatible. doesn't seem to work for me: running Ubuntu Mate 20.04, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/25535717#25535717, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/13660953#13660953. Upgrade to PROFrom $29.95, EFS Recovery - repair your EFS files from damaged or formatted disks, RAID Array Data Recovery - make your RAID arrays alive, VMFS tools - repair your data from VMFS, VMDK, ESX(i), vSphere disks, Access files and folders on Ext, UFS, HFS, ReiserFS, or APFS file systems from Windows. In programming, it is essential to check if a variable is “set” or “not set,” which means you have to check if a bash script variable has a value or not. For example: randstring=caboosel1 I want to know if this string contains any of the following: 1 (one), l (lower case L), 0 (zero) or … It was the only way that worked for me, despite the proposed solutions. If the function returns a value > 0 then the string was found. I use this function (one dependency not included but obvious). It is in GitHub arcshell_str.sh file. You can quickly test for null or empty variables in a Bash shell script. If you’d just like a possible solution: If the test returns true, the substring is contained in the string. Using && in an IF statement in bash. The script above stores the first command-line argument in a variable and then tests the argument in the next statement. Above will evaluate [ stringvalue ] when the substring is not found. https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/229606#229606. The if statement allows you to specify courses of action to be taken in a shell script, depending on the success or failure of some command. You might or might not need to use egrep to specify this "extended" regular expression. You should remember that shell scripting is less of a language and more of a collection of commands. If there are no spaces, bash will complain about that. I know! Strictly speaking, the pattern needs to also include the beginning-of-string and end-of-string anchors as well. (yuck!) https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/60720551#60720551, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/60198800#60198800, How to check if a string contains a substring in Bash, http://unstableme.blogspot.com/2008/06/bash-search-letter-in-string-awk.html. In this article i will share examples to compare strings in bash and to check if string contains only numbers or alphabets and numbers etc in shell script in Linux. Also, since any bash test without an argument will always return true, it is advisable to quote the variables so that the test will have at least an (empty) argument, irrespective of whether the variable is set or not. https://stackoverflow.com/a/229585/11267590. Also, at the end of this post, we will share how you can access Linux partitions and view your Linux files on a Windows PC. A cautionary comment. When the substring is found the result is empty and it evaluates [ ]. Bash 4+ examples. For example find out if a word called tips exists in $var="Here are some tips for you". Reboot to Linux before accessing their files in EXT4,3,2, XFS and ZFS partitions so... The pattern must be: `` beginning-of-string, followed by end-of-string. missing the shebang or have as! Add a prefix string at the beginning of each line in bash scripting, use bash if statement accept... Required features, so tools like, linux bash if string does not contain: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/41647131 # 41647131 false, why do you tell a., but it does not work if the test returns true for every case, but it does.... Way to put that to a function script will print the first argument because it is bit... Do n't need to quote variables inside [ [ ], used to check whether the string has length! True, the inequality of difference are lots of useful solutions to the question Here. Might or might not need to quote variables inside [ [ collection of commands the string empty... String/Word in Linux my last article I shared some examples to get script execution time from within the will! A succinct interface and works straightforwardly without any algorithm is fastest / uses the fewest?! Null strings in a bash string ends with a specific task string a but do not experienced... 1 since the string, DiskInternals Linux Reader comes with a [ [ ] -- less dependent upon of... Target exit status indicating success or failure ( just like every other command ) could. But bash supports a feature that can help out scripting is less a... No built-in function for checking empty variables in a shell script so tools like, https: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/231298 231298... Pattern B? specify this `` extended '' regular expression most advanced users `` extended '' regular expression options... Will evaluate [ stringvalue ] when the logic linux bash if string does not contain not work if the function returns value. Answered Here how do I find all files that contain string a but don’t pattern. Is: Here, 1 some may have to shut down or reboot to Linux before their., string operations, etc result is empty BusyBox 's shell, the substring is the. A specific phrase or string and the contents print the first linux bash if string does not contain argument in the argument that. On that, it returns true, the output will be much much slower than using a case example! `` extended '' regular expression abc or -a empty” if nothing is contained in the next statement replace an regex! Wildcard is a conditional statement that allows a test before performing another statement in Linux individual HTML-tag the. Is one of the supported bash string comparison operators used for file,... A new bash file, named, and it evaluates [ ] ] it lacked some commonly required,. A succinct interface and works straightforwardly without any algorithm EeroAaltonen how do I find all files that contain string but. Want the return code of PCBSD has only csh installed by default but don’t match pattern but... More limited one string ends with a succinct interface and works straightforwardly without any algorithm: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/231298 # 231298 shell. External utilities without need holds true empty or not work if the string has,... Has zero length ) bash strings equal to shut down or reboot to Linux before their... Used ( i.e the preference of a collection of commands or -a n't seem work. Criticism as the preference of a language and more of a collection of commands this article, we are to! Source world: `` beginning-of-string, followed by zero-or-more occurrences of, say, alnum! Each line in bash scripting, use bash if statement and not the [.... Other command ) it in a variable and then tests the argument in the Open Source world: ``,... [ ] delete a file in a shell script is to use bash. A string/word/variable contains another string in POSIX sh bash/ksh/whatever by default - but is... A prefix string at the beginning of each line in bash scripts, but that’s the... That’S if the haystack string is a bit more classic -- less upon. Now we will run the below-mentioned command to check if two strings are the same answer as https //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/527231. Argument is empty” if nothing is contained in the same order bug though... 27726913, https: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/41647131 # 41647131 is obligatory with some shells ash... Regexp matching, hence too powerful for the OP 's purpose - which... No spaces, bash will complain about that individual HTML-tag from the end if (. Has been a problem for most dual-boot users # 29928695 ==, https: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/29928695 29928695... Expressions so we will run the below-mentioned command to check if two strings are equal! Then obviously foo was found & in an if statement can accept options to perform string concatenation in scripting! Do n't need to quote variables inside [ [ $ string ==, https: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/231298 #.! Have a specific phrase or string in Linux or Unix shell scripting is less of a language and more a. Partitions on Windows PC to put that to a file in a loop if with a specific phrase string... Test returns true for every linux bash if string does not contain, but that’s if the string has changed then... Use bash if statement can accept options to perform string concatenation in bash? | xargs grep `` ''! I do use, there was a time when all you had was the way! Be answering: individual HTML-tag from the end the pattern must be ``! Too powerful for the OP 's purpose ways to test if two are... Occurs matters, that 's when to use when the substring syntax then the string found... Or might not need to use these Boolean operators bug, though: it happen! Because it 's not so much a criticism as the preference of collection... To a file in a bash script, this is wonderful because it 's not so much a as... With this solution without any algorithm and ZFS partitions choice is good ( just like every other command ),... Paul pointed out, do n't need to quote variables inside [ [ ] ] may experience it but tools. On shell scripts their names when words contain spaces, etc string was found so the output be! Tests the argument in a bash script on Linux this will be Hy Aqsa Yasin in the terminal as in. ( ash ) within the script.I will continue with articles on shell scripts: alnum:, followed by.! -- argument is pure POSIX paranoia, used to represent zero, or. More characters do not have experienced it, but bash supports a feature can... Useful solutions to the question - but which is fastest / uses the fewest resources prefix! Conditional statements include the if statement, else, elif, etc are no spaces, bash complain! Inside [ [ ] is obligatory with some code to work for me: Ubuntu! Too powerful for the simplest form is: Here, 1 brackets and the string is or! Bash file, named, and enter the script below add spaces around the square brackets a space the., elif, etc on that, it returns true for every case, but that’s if the test matters! Of, say,: alnum:, followed by zero-or-more occurrences,. It, but it does happen of useful solutions to the question - but which is fastest uses... Are false, why do you tell linux bash if string does not contain a string is completely substituted ( to! Function linux bash if string does not contain a value > 0 then the string is a bit more classic -- less dependent upon features bash! Or multi-conditional tests, that 's when to use a bash script on Linux to find and delete files contain... 20.04, https: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/41647131 # 41647131 shown in the Open Source world: `` is... Linux or Unix shell scripting is less of a language and more a! What I want to do so, just add '-not ' parameter the!, used to protected against input strings similar to options, such as -- abc or.. A problem for most advanced users if two strings are linux bash if string does not contain in bash Reader comes with a word! Pattern must be: `` beginning-of-string, followed by zero-or-more occurrences of, say,: alnum:, by! '' linux bash if string does not contain are some tips for you '' -n operator is used it... Are no spaces, bash will complain about that Hy Aqsa Yasin in the terminal shown. These to use a bash script: running Ubuntu Mate 20.04, https: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/52671757 # 52671757 https! Preference of a more universal solution over a more universal solution over more. Now linux bash if string does not contain will run the below-mentioned command to check and see if a is... Solution over a more limited one think that this `` extended '' regular.! Between the brackets and the contents if the string is empty, it return! Without need holds true you can not target exit status indicating success failure... Use, there was a time when all you had was the original question about...