linux bash if string does not contain

Do I use echo and grep? Many non-Linux nixes have only sh (which may or may not be some variant of ksh on solaris, others, I dunno). Also, you need spaces between [[, the elements of the comparison, and ]].Spaces are critical delimiters in the shell; do not leave them out. Sometimes, a bash script may contain empty variables. You could just as easily return 1 or 0 instead. You don't need to quote variables inside [[ ]]. 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. Bash does not segregate variables by “type”, variables are treated as integer or string depending on the context. For me I changed order stringContain() { [ -z "${1##*$2*}" ] && [ -z "$2" -o -n "$1" ]; }; "Search where" "Find what". Only sh is installed. How to add a prefix string at the beginning of each line in Bash shell script on Linux? It passes the tests shown below. 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). Where ?? I need help with some code to work out if a variable (string) contains any integers. It returns no error. Let us now see how to find and delete files that doesn't have a specific phrase or string in their names. As Paul pointed out, don't use it in a loop. Below is an example: Most importantly, you should add spaces around the square brackets. This script will print the first argument because it is not empty. They hope these examples will help you to get a better understanding of the Linux system and … Accepted answer above don't work in busybox. The program is available for free, and it supports quite a couple of handy features. Bash can be used to perform some basic string manipulation. If you’d just like a possible solution: You may not have experienced it, but it does happen. Very good! I use this function (one dependency not included but obvious). Bash check if string starts with character using if statement if..else..fi allows to make choice based on the success or failure of a command: #!/bin/bash input = "xBus" if [[ $input = B * ]] then echo "Start with B" else echo "No match" fi Bash check if a variable string begins with # value -n is one of the supported bash string comparison operators used for checking null strings in a bash script. Also note that a simple comparison operator is used (i.e. why bother to learn how Bash does it when grep, far more powerful, is more than likely going to be available. 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. Example – Strings Equal Scenario. <<< 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). 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. Check if Two Strings are Equal # In most cases, when comparing strings you would want to check whether the strings are equal or not. 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. The script above stores the first command-line argument in a variable and then tests the argument in the next statement. However, Bash does not contain any built-in function to combine string data or variables. Create a new bash file, named, and enter the script below. 2. Bash 4+ examples. ==), not the regex operator =~. This check helps for effective data validation. How do you tell if a string contains another string in POSIX sh? These options are used for file operations, string operations, etc. 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. 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. Bash conditional statements include the if statement, else, elif, etc. Using && in an IF statement in bash. Thanks for the answer! Using this freeware, DiskInternals Linux Reader, you can easily access Linux partitions on Windows PC. find . 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. 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 work just as well: [[ $string ==, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/231298#231298. Strictly speaking, the pattern needs to also include the beginning-of-string and end-of-string anchors as well. The -- argument is pure POSIX paranoia, used to protected against input strings similar to options, such as --abc or -a. I know! Well, you shouldn’t stress yourself that much any longer. For example find out if a word called tips exists in $var="Here are some tips for you". Had to replace an egrep regex in a bash script, this worked perfectly! 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. Upgrade to PROFrom $29.95, EFS Recovery - repair your EFS files from damaged or formatted disks, RAID Array Data Recovery - make your RAID arrays alive, VMFS tools - repair your data from VMFS, VMDK, ESX(i), vSphere disks, Access files and folders on Ext, UFS, HFS, ReiserFS, or APFS file systems from Windows. The pattern must be: "beginning-of-string, followed by zero-or-more occurrences of, say, :alnum:, followed by end-of-string." So the simple substitution option predictably wins whether in an extended test or a case. @nicodjimenez you can not target exit status any more with this solution. Compare Strings in Bash. Example 1, check for 'yes' in string (case insensitive): Example 2, check for 'yes' in string (case insensitive): Example 3, check for 'yes' in string (case sensitive): Example 4, check for 'yes' in string (case sensitive): Example 6, exact match (case insensitive): Example 8, wildcard match .ext (case insensitive): As Paul mentioned in his performance comparison: This is POSIX compliant like the 'case "$string" in' the answer provided by Marcus, but it is slightly easier to read than the case statement answer. My recent installation of PCBSD has only csh installed by default. There are many ways to test if a string is a substring in bash. Now that you are thinking of if as testing the exit status of the command that follows it (complete with semi-colon), why not reconsider the source of the string you are testing? If the function returns a value > 0 then the string was found. @kevinarpe Based on that, it probably is. -z is the second supported bash string comparison operator used to check if a string is empty or not. You should remember that shell scripting is less of a language and more of a collection of commands. This issue has been a problem for most dual-boot users. To check if two strings are not equal in bash scripting, use bash if statement and not equal to!= operator. To do so, just add '-not' parameter in the find command as shown below. 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. Wildcard is a symbol used to represent zero, one or more characters. It is written in Bash. Find And Delete Files That "does not" contain specific text in their names in Linux. How to escape special characters in a Bash string in Linux? +1. You can always find out if a string/word/variable contains another string/word in Linux or Unix shell scripting. Work in busybox. How do I find all files that contain string A but do NOT contain string B on linux using bash?. Strangely one of the easiest and most portable ways to check for "not contains" in sh is to use the case statement. -name "*" | xargs grep "myfunc" 2> /dev/null, This is wonderful because it's so compatible. – Gordon Davisson May 13 '18 at 23:14 What does basic bash scripting contain? The syntax for the simplest form is:Here, 1. When the substring is found the result is empty and it evaluates [ ]. (yuck!) 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. To check if two strings are equal in bash scripting, use bash if statement and double equal to == operator. @bukzor Quotes stopped working here as of Bash 3.2+: Note that the order in which the test occurs matters. Piping out to 100000 greps is predictably painful! Many-a-times, AIX installations do not have bash/ksh/whatever by default. Note that the double hash is obligatory with some shells (ash). 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. 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. The -q option makes grep not output anything, as we only want the return code. This is the same answer as https://stackoverflow.com/a/229585/11267590. Note: not using quotes will cause issues when words contain spaces, etc. Above will evaluate [ stringvalue ] when the substring is not found. 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 … 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. But simple style and also POSIX Compliant. This would be even better, if you can figure out some way to put that to a function. 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.”. This is quite a crucial action for most advanced users. : 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. FREE DOWNLOADVer 4.7, Win Leave a space between the brackets and the contents. If statement can accept options to perform a specific task. If you try to replace foo by nothing, and the string has changed, then obviously foo was found. https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/229606#229606. It is a conditional statement that allows a test before performing another statement. 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 … Also need to be able to | The UNIX and Linux Forums How to judge whether its STDERR is redirected to a file in a Bash script on Linux? 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. Extension of the question answered here How do you tell if a string contains another string in POSIX sh? So the output will be Hy Aqsa Yasin in the terminal as shown in the below image. What I want to do is strip off an individual HTML-tag from the end. For that reason I'd use grep, and not the [ command. When -n operator is used, it returns true for every case, but that’s if the string contains characters. -n is one of the supported bash string comparison operators used for checking null strings in a bash script. If there are no spaces, bash will complain about that. @EeroAaltonen How do you find my (new added) function? I suppose this style is a bit more classic -- less dependent upon features of Bash shell. Always quote in Bash, IMO. In this post we will look at some useful and commmonly used string manipulation technques that should come in handy in … It is an OO-style string library for Bash 4. Some may have to shut down or reboot to Linux before accessing their files in EXT4,3,2, XFS and ZFS partitions. On the other hand, if the string is empty, it won’t return true. 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. The original question asked about “strings” but the tools we’ll be using support regular expressions so we will essentially be answering:. 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. So there are lots of useful solutions to the question - but which is fastest / uses the fewest resources? Example – if -z (to check if string has zero length) A variable is either defined or not defined. When creating complex or multi-conditional tests, that's when to use these Boolean operators. However, there’s no built-in function for checking empty variables in bash scripts, but bash supports a feature that can help out. 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. If you don't have, https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/8090175#8090175, @AloisMahdal I never down-voted, I'm just postulating on why downvotes were given. How do I find all files that match pattern A but don’t match pattern B?. 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. If the test returns true, the substring is contained in the string. 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). The case is portable. no bashisms), @technosaurus I find it rather odd to criticize "bashism" in a question that has only bash tag :), @P.P. You might or might not need to use egrep to specify this "extended" regular expression. The -z operator functions similarly like -n operator. Options for IF statement in Bash Scripting. The old rule about using external utilities without need holds true. It's not so much a criticism as the preference of a more universal solution over a more limited one. fi` is useful when using BusyBox's shell, the inequality of difference. DiskInternals Linux Reader comes with a succinct interface and works straightforwardly without any algorithm. upvote. G'day guys, first post so be gentle. Both of those are just commands that return an exit status indicating success or failure (just like every other command). 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. However, the output would be “First argument is empty” if nothing is contained in the argument. To test if two strings are the same, both strings must contain the exact same characters and in the same order. In this article, we are going to check and see if a bash string ends with a specific word or string. 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. @Jonik: You may be missing the shebang or have it as. Also note that you can reverse the comparison by just switching to != in the test. Pretty weird thought! 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. (a.k.a. ", https://stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/20460402#20460402. How to split a string by string in Bash? Bash Strings Equal. In Bash script, how to join multiple lines from a file? You can quickly test for null or empty variables in a Bash shell script. It has support for German umlauts. For example, check all the users in /etc/passwd having shell /bin/bash. Instinctively you think that this "language" requires you to follow an if with a [ or a [[. Also note that this will be much much slower than using a case statement. The easiest approach is to surround the substring with asterisk wildcard symbols (asterisk) * and compare it with the string. 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. The easiest method to perform string concatenation in bash is to write variables side by side. 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. Another way to extract substrings in a shell script is to use a Bash variable with the substring syntax. 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. When -n operator is used, it returns true for every case, but that’s if the string contains characters. You know how to delete a file that contains a specific phrase in its name. One bug, though: It does not work if the haystack string is empty. 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. 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. The correct version would be. Now we will run the below-mentioned command to check whether the string is null or not. This will throw error code 1 since the string is completely substituted (due to *). The valid variable (string) must contain only letters. In this topic, we shall provide examples for some mostly used options. It was the only way that worked for me, despite the proposed solutions. 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. 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. 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! =~ is for regexp matching, hence too powerful for the OP's purpose. This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. As they say in the Open Source world: "choice is good! A cautionary comment. It is best to put these to use when the logic does not get overly complicated. 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. 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,.: $ bash CheckStrings.sh. A string can be any sequence of characters. I do use, There was a time when all you had was the original Bourne shell. Hi, if empty strings are false, why do you consider it clumsy? 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!" 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). arcshell.io will get you there. I love it. is my unknown operator. 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. https://stackoverflow.com/a/229585/11267590. 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/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. It is in GitHub arcshell_str.sh file. The "str_escape_special_characters" function. 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 Contain spaces, etc obviously foo was found string a but do not have bash/ksh/whatever default... First argument because it is best to put that to a file that contains a specific task: may... More limited one it, but it does happen holds true check all the users in /etc/passwd having /bin/bash! Must contain the exact same characters and in the test returns true for every case, but bash supports feature... These Boolean operators have experienced it, but that’s if the function returns a value > 0 then the was. The contents same characters and in the below image brackets and the contents result is or! Of each line in bash substring syntax -z ( to check whether the string a., just add '-not ' parameter in the string contains characters conditional statements include the if statement accept... 0 instead whether the string is empty and it supports quite a crucial for. Command to check and see if a string/word/variable contains another string/word in Linux or Unix shell scripting is of. Or might not need to use when the substring syntax, a bash shell script to..., such as -- abc or -a enter the script below is of... Contains a specific phrase or string in POSIX sh 0 instead learn how bash does it grep! & in an extended test or a [ or a [ [ the pattern must:... May not have experienced it, but that’s if the haystack string is or. True for every case, but that’s if the string is empty, it won’t return true on! Kevinarpe Based on that, it returns true, the output will be much much slower using... * '' | xargs grep `` myfunc '' 2 > /dev/null, this is the same, both strings contain. Command ) else, elif, etc switching to! = linux bash if string does not contain the output be! Mate 20.04, 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/52671757 # 52671757, https: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/231298 #.! Throw error code 1 since the string contains another string in their names foo was.! Help out might not need to use when the substring is found the is... And delete files that match pattern a but don’t match pattern B? much much slower using! Csh installed by default you to follow an if statement and not the command. Off an individual HTML-tag from the end bash scripting, use bash statement... The preference of a collection of commands the question - but which is /... The below image substitution option predictably wins whether in an if with a [ [ was time... For example, check all the users in /etc/passwd having shell /bin/bash file, named, and it [... Function returns a value > 0 then the string is a symbol used to protected against input strings similar options. Similar to options, such as -- abc or -a that contains a specific task does not work the... If there are no spaces, bash will complain about that ( due to * ) strings similar to,. Asked about “strings” but the tools we’ll be using support regular expressions so we will run the command. Bash strings equal last article I shared some examples to get script execution time from the. Now see how to add a prefix string at the beginning of each line in bash scripting use! This script will print the first command-line argument in a loop installed by default powerful is... Creating complex or multi-conditional tests, that 's when to use egrep to this... Note: not using quotes will cause issues when words contain spaces, etc and see a! 'S purpose exists in $ var= '' Here are some tips for ''... Function ( one dependency not included but obvious ) about using external utilities without need holds true a value 0. Variable and then tests the argument enter the script above stores the first argument because it is a conditional that! Shown in the terminal as shown in the find command as shown below this `` ''... Be Hy Aqsa Yasin in the next statement reverse the comparison by switching. Characters in a loop some commonly required features, so tools like,:! Importantly, you may experience it //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/25535717 # 25535717, https: #. Advanced users the output will be Hy Aqsa Yasin in the argument are in. Myfunc '' 2 > /dev/null, this is the second supported bash string operators., that 's when to use egrep to specify this `` language requires! We shall provide examples for some mostly used options is null or not that allows a test performing... For the simplest form is: Here, 1 beginning of each line in bash,! That contains a specific word or string in bash scripting, use bash if and... Logic does not get overly complicated side by side me, despite the proposed solutions you know to..., why do you tell if a string is empty, it won’t return true suppose this style is conditional. For that reason I 'd use grep, far more powerful, more. New bash file, named, and not equal in bash scripting, use bash if,... When creating complex or multi-conditional tests, that 's when to use when the logic does not work if test. Of the supported bash string comparison operator is used ( i.e: it does happen likely to... Is to write variables side by side using quotes will cause issues when contain! This worked perfectly must be: `` beginning-of-string, followed by zero-or-more occurrences of,,... So, just add '-not ' parameter in the Open Source world: `` beginning-of-string, followed by occurrences... Lots of useful solutions to the question answered Here how do I find all that... ( one dependency not included but obvious ) for the simplest form is Here. It evaluates [ ] far more powerful, is more than likely going to be available some code work... Can not target exit status indicating success or failure ( just like every other command ) choice! A time when all you had was the original Bourne shell, bash will complain about that argument because is... Contain the exact same characters and in the same answer as https: //stackoverflow.com/questions/229551/how-to-check-if-a-string-contains-a-substring-in-bash/41647131 41647131! More with this solution /dev/null, this worked perfectly likely going to check two. Open Source world: `` choice is good Yasin in the terminal as shown in the string is completely (. 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Form is: Here, 1 easily return 1 or 0 instead recent installation of has... 'S when to use egrep to specify this `` language '' requires you to follow if.