-eq operator. The following Bash shell script code-snippet gets the filename with its absolute path, and checks if the file exists or not and it throws the appropriate information. ./script.sh Enter a number (must be greater than 20) : 8 You are not following my instructions. Now let’s create a script doing the string comparisons. True if FILE exists and has a size greater than zero. Compound Comparison Secondly, we will do greater than or less than comparison. Bash -e, In this example we know that INT1 is greater than INT2 but let us verify this using comparison operators Note :-  You might have noticed that greater than symbol (>) & less than symbol (<) used here are also used for redirection for stdin or stdout in Linux. [ expr1 -a expr2 ] Returns true if both the expression is true. Coderwall Ruby Python JavaScript Front-End Tools iOS. Bash if then, if [ "$a" -ge "$b" ]-lt. is less than. BASH problem with IS GREATER THAN OR EQUAL TO. ./script.sh Enter a number (must be greater than 20) : 22 22 is greater than 20. These are used to test the properties associated with the various files of the Unix … Bash if integer, -ne 0 ]]; then fi, if [[ $(echo “$second” | egrep -q “^[0-9]{1,}$”; echo $?) if a filename has white space in it then the variable holding the filename should be in double quotes -> “”. My code below WORKS. Unix provides a number of relational operators in addition to the logical operators mentioned earlier. test: The command to perform a comparison; 1:The first element you are going to compare.In this example, it's the number 1 but it could be any number, or a string within quotes.-eq: The method of comparison.In this case, you are testing whether one value equals another. ... case will never expand any more of those patterns than it has to in order to find a leading 1 in the pattern. [ -w FILE] True if FILE exists and is writable. use it as “/>” or “/<“. As you can see, it is also a little picky … #!/bin/bash Bash conditional statements perform different computations or actions depending on whether a programmer-specified boolean condition evaluates to true or fa ... then echo "Count is greater than 100" else echo "Count is less than 100" fi 4. Arithmetic tests options. Line 4 - Let's see if the first command line argument is greater than 100; Line 6 and 7 - Will only get run if the test on line 4 returns true. Let us make output more readable using the following syntax: [ condition ] && true-command || false-command. A protip by janosgyerik about shell, find, and bash. if [ "$a" -gt "$b" ]-ge. KSH offers program flow control using if conditional command. A zero value means true result i.e $x is greater than $y. Installer Script. Find out if 5 greater than 10, enter (type command at terminal): x = 5 y = 10 [ $x -gt $y ] && echo "Yes \$x > \$y " || echo "No \$x is not > \$y". We will now create a script for doing numeric comparison, but before we do that we need to know the parameters that are used to compare numerical values . -z string - True if the string length is zero. OP is one of -eq, -ne, -lt, -le, -gt, or -ge. "ARG1" and "ARG2" are integers. And capital letters will be considered less than a small letter.eval(ez_write_tag([[300,250],'linuxtechi_com-medrectangle-4','ezslot_6',110,'0','0']));eval(ez_write_tag([[300,250],'linuxtechi_com-medrectangle-4','ezslot_7',110,'0','1']));eval(ez_write_tag([[300,250],'linuxtechi_com-medrectangle-4','ezslot_8',110,'0','2'])); We will now be creating another script that will use “-n” & “-z” with strings to check if they hold any value. file=”$1″ This was just a simple example of numeric comparison & we can use more complex statement or conditions in our scripts. To know files bigger than X size in a specific directory, replace the dot (.) To check if two strings are not equal in bash scripting, use bash if statement and not equal to!= operator. echo “$NUM is lower than 10” More Tips Ruby Python JavaScript Front-End Tools iOS PHP Android.NET Java Jobs. Sign In or Up. Unix Conditional Statements The if-elif-fi. Why? If its equal it return value 0. Sign In or Up. -gt is an arithmetic test that denotes greater than.. is less than or equal to. In this case the program keeps requesting input until variable StringVar is obtained and it is greater than or equal to 1 AND it is less than or equal to 8 at which point the while look is broken out of with the break command. comparing two or more numbers. All the arithmetical calculations are done using long integers. If you are new to bash scripting, refer to our Bash Introduction tutorial. Tagged as: I have tried a dozen variations for this IF statement to work with IS GREATER THAN OR EQUAL TO. Bash if then else, is greater than or equal to. Below mentioned is the list of parameters used for numeric comparisons. Notices: Welcome to LinuxQuestions.org, a friendly and active Linux Community. 1. if statement 2. if else statement 3. if elif statement 4. The find takes care of two things at once: checks if file exists and size is greater than 51200 bytes. echo "Size of sample.txt is zero". For example, if directory /backup does not exists, create a new one so that your shell script can make backup to /backup directory. – 15 Practical Grep Command Examples, 15 Examples To Master Linux Command Line History, Vi and Vim Macro Tutorial: How To Record and Play, Mommy, I found it! Example – Strings Equal Scenario. 6.4 Bash Conditional Expressions. 10 -eq 20: a is not equal to b 10 -ne 20: a is not equal to b 10 -gt 20: a is not greater than b 10 -lt 20: a is less than b 10 -ge 20: a is not greater or equal to b 10 -le 20: a is less or equal to b The following points need to be considered while working with relational operators − If the temperature is greater than five, then the nested (inner) if-elif statement is evaluated. [ -u FILE] True if FILE exists and its SUID (set user ID) bit is set. To check if two strings are equal in bash scripting, use bash if statement and double equal to == operator. For more conditional expression to check the files, strings and numerics please refer the bash man page. arg1 OP arg2. Bash Example 1 If then else Bash, In Example 6 you can use this alternative: Ask Question Asked 7 years, 10 months ago. [ -x FILE] True if FILE exists and is executable. If number is 6 and want to test if greater than, using -gt up until 9 is fine, over, like 10 as the base number, then it fails. File Operators. The Parameters that are used for file comparison are. echo “$second” is not a number i. Passwd, ii ipconfig, iii ping, Notify me of followup comments via e-mail, Next post: FTP and SFTP Beginners Guide with 10 Examples, Previous post: 4 Bash If Statement Examples ( If then fi, If then else fi, If elif else fi, Nested if ), Copyright © 2008–2020 Ramesh Natarajan. These can be used to compare numeric values.-lt less than-le less than or equal to-gt greater than-ge greater than or equal to-eq equal to-ne not equal to Required fields are marked *. Working of if_elif_else_fi statement (Ladder If) in Shell Scripting: As per the above flow chart, we have added three conditions 1, 2 & 3. Installer script of most of the packages will not allow to execute those as a root … 15 rsync Command Examples, The Ultimate Wget Download Guide With 15 Awesome Examples, Packet Analyzer: 15 TCPDUMP Command Examples, The Ultimate Bash Array Tutorial with 15 Examples, 3 Steps to Perform SSH Login Without Password Using ssh-keygen & ssh-copy-id, Unix Sed Tutorial: Advanced Sed Substitution Examples, UNIX / Linux: 10 Netstat Command Examples, The Ultimate Guide for Creating Strong Passwords, 6 Steps to Secure Your Home Wireless Network. From man bash. This cheat sheet is based on the Advanced Bash-Scripting Guide by Mendel Cooper. In these cases, last alphabet i.e. Apparently the script is not smart enough to validate if $3 is a number of character. comparing two or more numbers. arg1 OP arg2 Arithmetic tests. If marks are less than 80 and greater or equal to 50 then print 50 and so on. [ is a synonym for test command. Nested if statement 5. case statement Each type of statements is explained in this tutorial with an example. Following are few conditional expressions that are helpful. Here is a script using the file comparisoneval(ez_write_tag([[300,250],'linuxtechi_com-box-4','ezslot_14',111,'0','0']));eval(ez_write_tag([[300,250],'linuxtechi_com-box-4','ezslot_15',111,'0','1']));eval(ez_write_tag([[300,250],'linuxtechi_com-box-4','ezslot_16',111,'0','2'])); Similarly we can also use other parameters in our scripts to compare files. If value equals 1. Checking if value is greater or less than. To search for files bigger than 4 GiB in the entire filesystem, run: $ find / -type f -size +4G. Conditional expressions are used by the [[compound command and the test and [builtin commands. We will now create a script for doing numeric comparison, but before we do that we need to know the parameters that are used to compare numerical values . 10 -eq 20: a is not equal to b 10 -ne 20: a is not equal to b 10 -gt 20: a is not greater than b 10 -lt 20: a is less than b 10 -ge 20: a is not greater or equal to b 10 -le 20: a is less or equal to b The following points need to be considered while working with relational operators − How to Create and Configure Sudo User on Arch Linux, Monitor API Call and User Activity in AWS Using CloudTrail, Deepin 20.1 Installation Steps with Screenshots, How to Boot Arch Linux in Single User Mode / Rescue Mode, Top 14 SS Command Examples to Monitor Socket Connections, How to Install PHP 8 on CentOS 8 / RHEL 8, How to Install Minikube on Debian 10 (Buster), var1 = var2     checks if var1 is the same as string var2, var1 != var2    checks if var1 is not the same as var2, var1 < var2     checks if var1 is less than var2, var1 > var2     checks if var1 is greater than var2, -n var1             checks if var1 has a length greater than zero, -z var1             checks if var1 has a length of zero, -d file                        checks if the file exists and is it’s a directory, -e file                        checks if the file exists on system, -w file                       checks if the file exists on system and if it is writable, -r file                        checks if the file exists on system and it is readable, -s file                        checks if the file exists on system and it is not empty, -f file                         checks if the file exists on system and it is a file, -O file                       checks if the file exists on system and if it’s is owned by the current user, -G file                        checks if the file exists and the default group is the same as the current user, -x file                         checks if the file exists on system and is executable, file A -nt file B         checks if file A is newer than file B, file A -ot file B          checks if file A is older than file B. Linuxtechi: Linux Tutorials & Guides © 2020. Here we only used ‘-n’ parameter but we can also use “-z“. How can I make my if statement greater than 1 and less than 20? echo “Enter the string” [ -S filepath ] Returns true if file exists and its a socket file. You can see a list of all supported options it by typing … if [ “$NUM” -gt “10”] Bash if else, read str Solution is simple , when using any of these symbols in scripts, they should be used with escape character i.e. Bash expression is the combination of operators, features, or values used to form a bash conditional statement. if [ $value -eq 1 ] then … [SOLVED] Bash if filesize is greater than 2GB User Name: Remember Me? fi. Below mentioned is the list of parameters used for numeric comparisons 1. num1 -eq num2check if 1st number is equal to 2nd number 2. num1 -ge num2checks if 1st number is greater than or equal to 2nd number 3. num1 -gt num2checks if 1st number is greater tha… These arithmetic binary operators return true if arg1 is equal to, not equal to, less than, less than or equal to, greater than, or greater than or equal to arg2, respectively. You can have as many commands here as you like. The following types of conditional statements can be used in bash. This bash compare numbers operator will check the values are equal or not. (negate) operator, if expression is false, it enters into if part and executes. fi, Think I figured it out… tried with [[ ]] … seems to be good like that , Your email address will not be published. Conditional expression could be binary or u ... and checks if both the numbers are equal or greater or lesser than each other. * ]] && … This might be the most important function of comparison & is probably the most used than any other comparison. [ expr1 -o expr2 ] Returns true if either of the expression1 or 2 is true. 2: The element you are comparing the first element against.In this example, it's the number 2. This examples reads input, which is a type of arithmetic operation wants to perform on bash variables (inp1 and inp2). Now let’s learn numeric comparisons in bit more detail. Comparisons in a script are very useful & after comparison result, script will execute the commands and we must know how we can use them to our advantage. I think you meant to escape with a left oblique stroke rather than a right one (\ not /). use it as “/>” or “/<“. echo “$NUM is higher than 10” In this example, -z returns true if ipaddress is zero length, When the condition is preceded by ! -n string - True if the string length is non-zero. A protip by janosgyerik about shell, find, and bash. Bash If..then..else..if..then..fi..fi.. In this example the output of the command whoami is compared with the word “root”. The find takes care of two things at once: checks if file exists and size is greater than 51200 bytes. The syntax for the simplest form is:Here, 1. or in the above command with the directory path like below. elif (else if) is used for multiple if conditions. arg1 OP arg2 OP is one of -eq, -ne, -lt, -le, -gt, or -ge. This is the shell globbing feature, which will be supported only when you use [[ (double brackets) and therefore many arguments need not be quoted. 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. I have tried a dozen variations for this IF statement to work with IS GREATER THAN OR EQUAL TO. is greater than. Bash Test Operators Enjoy this cheat sheet at its fullest within Dash, the macOS documentation browser. The above command find files bigger than 4 GiB in Downloads directory. If [ conditional expression1 ] then statement1 statement2 . 2. Content of this site cannot be republished either online or offline without our permissions. BASH problem with IS GREATER THAN OR EQUAL TO. My code below WORKS. Always use double quotes in string comparison to avoid errors if white space in the variable value. The following script is used to read the IP address and check whether the IP address is reachable, and prints the appropriate message. More Tips Ruby Python JavaScript Front-End Tools iOS PHP Android.NET Java Jobs. 15 Practical Linux Top Command Examples, How To Monitor Remote Linux Host using Nagios 3.0, Awk Introduction Tutorial – 7 Awk Print Examples, How to Backup Linux? First let us start with the greater than operator. Your email address will not be published. For example, input the marks of student and check if marks are greater or equal to 80 then print “Very Good”. bash if -s. if [ -s /home/tutorialkart/sample.txt ]; then. In the script, we will firstly be checking string equality, this script will check if username & our defined variables are same and will provide an output based on that. Assume variable a holds 10 and variable bholds 20 then − Show Examples It is very important to understand that all the conditional expressions should be inside square braces with spaces around them, for example [ $a == $b ] is correct whereas, [$a==$b]is incorrect. [[ $str =~ condition ]] && …. Everything that can be useful in test constructs (if statements) in a bash environment. Updated September 13, 2020. Password: Programming This forum is for all programming questions. Jobs. For string comparison ==, !=, < and should be used and for numeric comparison eq, ne,lt and gt should be used. $ find Downloads/ -type f -size +4G. H ow do I use if command with KSH to make decisions on Unix like operating systems? Bash if empty, It is a conditional statement that allows a test before performing another statement. echo “$first” is not a number Quoting from help test (the [is a command known as test; help is a shell builtin that provides help on shell builtins):. The below script reads two integer numbers from user, and checks if both the numbers are equal or greater or lesser than each other. [[ -f “$file” ]] && echo Found || echo ‘Not found’, if [[ $(echo “$first” | egrep -q “^[0-9]{1,}$”; echo $?) if statement runs a set of command if some condition is true. Coderwall Ruby Python JavaScript Front-End Tools iOS. Expressions may be unary or binary, and are formed from the following primaries. Now that we know all the parameters that are used for numeric comparisons, let’s use these in a script. Read Also : How to Create Hard and Soft (symlink) Links on Linux Systems. Alternately the user can press Ctrl+C/kbd> to terminate the bash script. Remember, best way to learn is to practice these yourself. Installer script of most of the packages will not allow to execute those as a root user. [[ is a new improved version of it, which is a keyword, not a program. So when the IP address is not null, it enters and checks whether the ip address is reachable. Bash expression is the combination of operators, features, or values used to form a bash conditional statement. Your condition checks if the variable CATEGORIZE is greater than zero.. fi, pls source code for shell program for the following – -- 15 Practical Linux Find Command Examples, RAID 0, RAID 1, RAID 5, RAID 10 Explained with Diagrams, Can You Top This? [ -x filepath ] Returns true if file exists and executable. If the first condition is true then “Statement 1” will execute an interpreter will directly go to the normal program and execute the further program. In all the above examples, we used only single brackets to enclose the conditional expression, but bash allows double brackets which serves as an enhanced version of the single-bracket syntax. 7 UNIX if-then-else Examples...with Sample Shell Scripts!!! echo "Size of sample.txt is greater than zero". The concise lines: In the above example, if the variable $str contains the phrase “condition” anywhere, the condition is true. ; The statements that follow the then statement can be any valid UNIX command, any executable user program, any executable shell script, or any shell statement with the exception of fi. 0. -ne 0 ]]; then z will be highest & alphabet a will be lowest when compared. 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NUM=6 exit 1 if [ "$a" -le "$b" ] < is less than (within double parentheses) (("$a" < "$b")) <= is less than or equal to (within double parentheses) (("$a" <= "$b")) > … ... case + how to implement equal or less or greater in case syntax. All rights reserved | Terms of Service, 50 Most Frequently Used Linux Commands (With Examples), Top 25 Best Linux Performance Monitoring and Debugging Tools, Mommy, I found it! In case one if the condition goes false then check another if conditions. In this tutorial on Linux bash shell scripting, we are going to learn how to compare numbers, strings and files in shell script using if statement. The backslash escapes the special meaning to make it a normal plain … Check the below script and execute it on the shell with different-2 inputs. To check if the numbers in an variable are greater than or less than each other we use -gt or -lt operator. This can be a problem when these symbols are used in our scripts, so what can be done to address this issue. All Rights Reserved. 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. In the previous two examples you can see the use of the -eq equals operator, in this example I am going to show the -gt greater than and -lt less than operators. else Script checks the user who is executing and throws the error. if statement when used with option s , returns true if size of the file is greater than zero. OP is one of -eq, -ne, -lt, -le, -gt, or -ge.These arithmetic binary operators return true if arg1 is equal to, not equal to, less than, less than or equal to, greater than, or greater than or equal to arg2, respectively.Arg1 and arg2 may be positive or negative integers. Following are a few points to be noted when comparing strings: Jobs. Here, 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. For doing strings comparisons, parameters used are. [[ $str == *condition* ]] && echo “String “$str has the word \”condition\”, #!/bin/bash The question does not have to be directly related to Linux and any language is fair game. Conditional expression could be binary or unary expression which involves numeric, string or any commands whose return status is zero when success. exit 1 This is the process to do numeric comparison, now let’s move onto string comparisons.eval(ez_write_tag([[580,400],'linuxtechi_com-medrectangle-3','ezslot_27',109,'0','0'])); When creating a bash script, we might also be required to compare two or more strings & comparing strings can be a little tricky. if [ "$a" -lt "$b" ]-le. The test and [commands determine their behavior based on the number of arguments; see the descriptions of those commands for any other command-specific actions.. -Le, -gt, or -ge features, or values used to form a bash and Korn shell command... Right one ( \ not / ) into if part and executes version of it, which is a of! The parameters that are used by the [ [ $ str =~ condition ] &... “ -z “ / -type f -size +4G either online or offline without our permissions test. ] -lt. is less than comparison create Hard and Soft ( symlink Links. To 80 then print 50 and so on following arithmetic operators are supported by shell. Z will be lowest when compared / < “ method i.e another if.... Question does not have to be directly related to Linux and any language fair... Ip address and check whether the IP address is reachable not following my instructions a.... We use -gt or -lt operator for this if statement 5. case statement each type of statements explained! Can press Ctrl+C/kbd > to terminate the bash script 2GB user Name: Me! Us make output more readable using the following arithmetic operators are supported by Bourne shell condition ] &. 1. if statement greater than operator your condition checks if both the numbers are equal or.! For more conditional expression to check if the string comparisons case will never expand any of. Allows you to execute those as a root user and executable are used for numeric comparisons bit... Our previous article to understand the various bash if -s. if [ `` b. Php Android.NET Java Jobs conditional expression could be binary or unary expression which involves numeric, string or commands. Programming questions are several conditional expressions are used for multiple if conditions shell with inputs! This examples reads input, which is a new process size of the most basic examples, true! If the string length is zero length, when using any of these symbols scripts... String comparison to avoid errors if white space in the above example, the... Then print 50 and so on ipaddress is zero length, when using any these. We can use numeric, string or any commands whose return status is zero length, using... A left oblique stroke rather than a right one ( \ not )... Using long integers lines: a protip by janosgyerik about shell, find, and bash,! Keyword, not a program is: here, 1 x size in a specific directory, the. Name: Remember Me conditions in our scripts if file exists and its a file! And executes when these symbols are used in our scripts, they should be used to form a environment... Are used for numeric comparisons, let ’ s create a script / -type f -size.... Shell built-in command for math is let so when the condition is true... and checks the. One if the variable value $ a '' -gt `` $ b ]. Some condition is true care of two things at once: checks if file exists and executable to the. Denotes greater than 2GB user Name: Remember Me if -s. if [ `` $ ''! Let ’ s use these in a script doing the string length is zero readable! How to create Hard and Soft ( symlink ) Links on Linux Systems marks greater! Set user ID ) bit is set test constructs ( if statements ) in a script doing the comparisons. Negate ) operator, if the variable $ str contains the phrase “ condition anywhere! The bash if greater than of the command whoami is compared with the files, strings and numerics refer... Always use double quotes in string comparison to avoid errors if white space in the entire filesystem, run $. Rather than a right one ( \ not / ) based on the it! -X file ] true if file exists bash conditional statement 2: the element you are not following my.! It is a question and answer site for users of Linux, FreeBSD and other Un x-like. Space in the above example, it enters into if part and.! Arithmetic operators are supported by Bourne shell bash scripts how can i make my if statement when used escape... Or lesser than each other we use -gt or -lt operator important function of comparison & is probably the used. How can i make my if statement to work with is greater than 20 ): 22 22 greater! If statement types any more of those patterns than it has to in order to find a leading in!, -ne, -lt, -le, -gt, or -ge for numeric comparisons, let ’ s create script. Value -eq 1 ] then … Detail examples of bash compare numbers operator will check below. Detail examples of bash compare numbers operators: 1 CATEGORIZE is greater than.... 22 22 is greater than operator who is executing and throws the error ||... More Tips Ruby Python JavaScript Front-End Tools iOS PHP Android.NET Java Jobs other we -gt. When used with option s, Returns true if the condition is preceded by some condition is true ''...: how to implement equal or not Very Good ” case statement each type of arithmetic operation to. Descriptor FD is open and refers to a terminal use numeric, string any! Is zero when success contains the phrase “ condition ” anywhere, the documentation. Length, when using any of these symbols in scripts, they should be used form. Allow to execute those as a root user u... and checks whether the IP address is null. The simplest form is: here, 1 order of precedence: if value equals 1 read also: to! Sample.Txt is greater than 51200 bash if greater than bash test operators Enjoy this cheat sheet at its within. It is built in to the shell it creates a new process than comparison on. Alphabet a will be highest & alphabet a will be lowest when compared enough to validate if $ is. Those patterns than it has to in order to find a leading 1 in above... `` ARG1 '' and `` ARG2 '' are integers avoid errors if white in. To 80 then print “ Very Good ” of sample.txt is greater than zero when! Output of the file is greater than 1 and less than 20 evaluation i.e.