{"id":15016,"date":"2023-08-02T10:44:06","date_gmt":"2023-08-02T10:44:06","guid":{"rendered":"https:\/\/linuxsimply.com\/?p=15016"},"modified":"2024-01-04T09:36:44","modified_gmt":"2024-01-04T09:36:44","slug":"bash-check-variable-value","status":"publish","type":"post","link":"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/","title":{"rendered":"How to Check Variable Value Using Bash Scripts? [5 Cases]"},"content":{"rendered":"<p style=\"text-align: justify;\">In Bash scripts, inspecting and assessing variables&#8217; value is a fundamental skill that empowers developers to write more sophisticated and reliable scripts. Checking variable values allows us to <strong>make informed decisions<\/strong>, <strong>validate user input<\/strong>, and <strong>tailor script behavior <\/strong>based on different scenarios. There are several or even, thousands of user case scenarios to check the variable value in a different context, such as checking whether the variable value is defined or contains a specific value or datatype.<\/p>\n<p style=\"text-align: justify;\">However, in this article, I will discuss <strong>five <\/strong>different cases to assist how to check the variable value in the bash script.<\/p>\n<div class=\"su-button-center\"><a href=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/practice-files_bash-check-variable-value.zip\" class=\"su-button su-button-style-default\" style=\"color:#000000;background-color:#E8F9FF;border-color:#bac8cc;border-radius:56px\" target=\"_blank\" rel=\"noopener noreferrer\"><span style=\"color:#000000;padding:8px 26px;font-size:20px;line-height:30px;border-color:#effbff;border-radius:56px;text-shadow:0px 0px 0px #000000\"><i class=\"sui sui-download\" style=\"font-size:20px;color:#1AA1D6\"><\/i> Practice Files to Check Bash Variable Value<\/span><\/a><\/div>\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_82_2 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 eztoc-toggle-hide-by-default' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#5_Examples_to_Check_Variable_Value_Using_Bash_Script\" >5 Examples to Check Variable Value Using Bash Script<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#1_Check_If_a_Variable_is_Defined_in_Bash_Script\" >1. Check If a Variable is Defined in Bash Script<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#2_Verify_Whether_a_Variable_Has_a_Value_in_a_Bash_Script\" >2. Verify Whether a Variable Has a Value in a Bash Script<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#3_Check_if_a_Variable_Contains_a_Number_in_Bash\" >3. Check if a Variable Contains a Number in Bash<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#4_Verify_Whether_Variable_Equals_to_0_in_a_Bash_Script\" >4. Verify Whether Variable Equals to 0 in a Bash Script<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#5_Check_a_Variable_Contains_Text_String_Rather_Than_Integer_Value\" >5. Check a Variable Contains Text String Rather Than Integer Value<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#Conclusion\" >Conclusion<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#People_Also_Ask\" >People Also Ask<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#How_to_check_a_variable_value_in_bash\" >How to check a variable value in bash?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#Does_bash_have_variable_types\" >Does bash have variable types?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#How_to_check_numeric_value_in_Bash\" >How to check numeric value in Bash?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#How_to_read_a_value_in_Bash\" >How to read a value in Bash?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/check-value\/#How_to_check_string_length_0_in_Bash\" >How to check string length 0 in Bash?<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"5_Examples_to_Check_Variable_Value_Using_Bash_Script\"><\/span>5 Examples to Check Variable Value Using Bash Script<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">When writing <strong>complex scripts <\/strong>or programs, it&#8217;s essential to ensure that variables hold the <strong>expected values<\/strong>. By checking variable values during the execution of the script, you can quickly <strong>identify <\/strong>any <strong>unexpected <\/strong>or <strong>incorrect values<\/strong>, making it easier to <strong>debug <\/strong>and <strong>fix issues<\/strong>.<\/p>\n<p style=\"text-align: justify;\">In this article, I am going to demonstrate <strong>five <\/strong>different examples of checking the variable value using the bash script. So let\u2019s start.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"1_Check_If_a_Variable_is_Defined_in_Bash_Script\"><\/span>1. Check If a Variable is Defined in Bash Script<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">In Bash scripting, you can check if a variable is defined (whether it has been assigned a value). You can pass the <code class=\"\" data-line=\"\">-z<\/code> option to the <code class=\"\" data-line=\"\">if<\/code> command or <strong>conditional expression <\/strong>to check the variable. Here&#8217;s a sample code to accomplish the task:<\/p>\n<pre><code class=\"language-bash\" data-line=\"\">#!\/bin\/bash\n\n# Check if the variable is defined\nif [ -z ${variable+x} ]; then\n\u00a0\u00a0\u00a0 echo &quot;The variable is not defined.&quot;\nelse\n\u00a0\u00a0\u00a0 echo &quot;The variable is defined.&quot;\nfi<\/code><\/pre>\n<div class=\"su-box su-box-style-default\" id=\"\" style=\"border-color:#aeb0b3;border-radius:0px;max-width:none\"><div class=\"su-box-title\" style=\"background-color:#E1E3E6;color:#000000;border-top-left-radius:0px;border-top-right-radius:0px\"> EXPLANATION<\/div><div class=\"su-box-content su-u-clearfix su-u-trim\" style=\"border-bottom-left-radius:0px;border-bottom-right-radius:0px\">\n<p>The script uses the <code class=\"\" data-line=\"\">-z<\/code> option within an <code class=\"\" data-line=\"\">if statement<\/code>, along with parameter expansion. The expression <code class=\"\" data-line=\"\">${variable+x}<\/code> checks if the variable, <strong>variable <\/strong>is set, returning the value of <strong>x<\/strong> if it is <strong>set<\/strong>, and an <strong>empty string <\/strong>if it&#8217;s not. The <strong>-z<\/strong> <strong>option <\/strong>then checks if the result of the parameter expansion is an <strong>empty string<\/strong>. If the variable is not defined, the script prints &#8220;The variable is not defined.&#8221; to the console. Otherwise, if the variable is defined, it prints &#8220;The variable is defined.&#8221; to the console.<\/p>\n<\/div><\/div>\n<p style=\"text-align: justify;\"><img fetchpriority=\"high\" decoding=\"async\" class=\"aligncenter wp-image-15019 size-full\" src=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/1.-Check-If-Bash-Variable-Defined-in-Script.png\" alt=\"Check If Bash Variable Defined in Script\" width=\"612\" height=\"163\" srcset=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/1.-Check-If-Bash-Variable-Defined-in-Script.png 612w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/1.-Check-If-Bash-Variable-Defined-in-Script-300x80.png 300w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/1.-Check-If-Bash-Variable-Defined-in-Script-766x204.png 766w\" sizes=\"(max-width: 612px) 100vw, 612px\" \/>As the variable is not defined in the given <strong>Bash <\/strong>code, the output returns \u201cThe variable is not defined\u201d upon executing the <code class=\"\" data-line=\"\">var_defined.sh<\/code> bash file in the command line.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"2_Verify_Whether_a_Variable_Has_a_Value_in_a_Bash_Script\"><\/span>2. Verify Whether a Variable Has a Value in a Bash Script<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">In Bash scripts, it&#8217;s often necessary to verify if a variable holds a value or is <strong>empty<\/strong>, especially when handling user input or working on projects that require specific data. Several approaches can be used to perform such checks in Bash.<\/p>\n<p style=\"text-align: justify;\">Here, I have provided a bash script to verify whether a variable has a value in it. Check this out and don\u2019t forget to run the script on your own machine:<\/p>\n<pre><code class=\"language-bash\" data-line=\"\">#!\/bin\/bash\nvariable=\n\n#checking if the variable contains any value\nif [ x&quot;${variable}&quot; == &quot;x&quot; ]; then\n\u00a0\u00a0\u00a0\u00a0 echo &quot;No value found for the variable&quot;\n\u00a0 else\n\u00a0\u00a0\u00a0\u00a0 echo &quot;Value found for the variable&quot;\n\u00a0 fi<\/code><\/pre>\n<div class=\"su-box su-box-style-default\" id=\"\" style=\"border-color:#aeb0b3;border-radius:0px;max-width:none\"><div class=\"su-box-title\" style=\"background-color:#E1E3E6;color:#000000;border-top-left-radius:0px;border-top-right-radius:0px\"> EXPLANATION<\/div><div class=\"su-box-content su-u-clearfix su-u-trim\" style=\"border-bottom-left-radius:0px;border-bottom-right-radius:0px\">\n<p>Initially, the variable is initialized with an <strong>empty value<\/strong>. The <code class=\"\" data-line=\"\">if statement<\/code> then checks whether the <strong>variable is empty <\/strong>using the condition <code class=\"\" data-line=\"\">[ x&quot;${variable}&quot; == &quot;x&quot; ]<\/code>. To handle cases where the variable is <strong>empty <\/strong>or <strong>not set<\/strong>, the variable is prefixed with <strong>x<\/strong> within the comparison. If the variable is indeed <strong>empty<\/strong>, the script will execute the code block within the <strong>if statement<\/strong>, printing &#8220;No value found for the variable&#8221; to the standard output. Conversely, if the variable contains a value, the script executes the code block within the <strong>else statement<\/strong>, printing &#8220;Value found for the variable&#8221; to the console.<\/p>\n<\/div><\/div>\n<p><img decoding=\"async\" class=\"aligncenter wp-image-15020 size-full\" src=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/2.-Verify-Whether-a-Variable-has-a-Value-in-a-Bash-Script.png\" alt=\"Verify Whether a Variable has a Value in a Bash Script\" width=\"621\" height=\"174\" srcset=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/2.-Verify-Whether-a-Variable-has-a-Value-in-a-Bash-Script.png 621w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/2.-Verify-Whether-a-Variable-has-a-Value-in-a-Bash-Script-300x84.png 300w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/2.-Verify-Whether-a-Variable-has-a-Value-in-a-Bash-Script-767x215.png 767w\" sizes=\"(max-width: 621px) 100vw, 621px\" \/><\/p>\n<p style=\"text-align: justify;\">As the <strong>variable <\/strong>does not contain any value, the script returns \u201cNo value found for the variable\u201d in the command line.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"3_Check_if_a_Variable_Contains_a_Number_in_Bash\"><\/span>3. Check if a Variable Contains a Number in Bash<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">In Bash, variables are treated as character <strong>strings <\/strong>and <strong>arithmetic operations <\/strong>can be performed on them, even when they contain <strong>numeric data<\/strong>. However, before conducting arithmetic operations, it is essential to ensure that the variable holds a valid number. To verify this, you need to check that the value comprises only digits ranging from <strong>0 <\/strong>to <strong>9<\/strong>.<\/p>\n<p style=\"text-align: justify;\">Using regular expression with an <strong>equal tilde operator <\/strong><code class=\"\" data-line=\"\">=~<\/code> is one of the easiest ways to check whether the variable contains a number or not. To do the same use the following script:<\/p>\n<pre><code class=\"language-bash\" data-line=\"\">#!\/bin\/bash\nread -p &quot;Enter a number: &quot; var\n\n#Emplyoing the if statement with a regular expression to verify the numeric value\nif [[ $var =~ ^[0-9]+$ ]]; then\n\u00a0\u00a0 echo &quot;${var} is a number&quot;\nelse\n\u00a0\u00a0 echo &quot;${var} is not a number&quot;\nfi<\/code><\/pre>\n<div class=\"su-box su-box-style-default\" id=\"\" style=\"border-color:#aeb0b3;border-radius:0px;max-width:none\"><div class=\"su-box-title\" style=\"background-color:#E1E3E6;color:#000000;border-top-left-radius:0px;border-top-right-radius:0px\"> EXPLANATION<\/div><div class=\"su-box-content su-u-clearfix su-u-trim\" style=\"border-bottom-left-radius:0px;border-bottom-right-radius:0px\">\n<p>Initially, the code takes the user input <strong>var <\/strong>variable using the <code class=\"\" data-line=\"\">read -p<\/code> command. Accompanied by the if statement, the regular expression <code class=\"\" data-line=\"\">^[0-9]+$<\/code> verifies whether the entire string, representing the user&#8217;s input stored in the variable var, consists solely of <strong>numeric digits <\/strong>from <strong>0 <\/strong>to <strong>9<\/strong>. If so, it returns <code class=\"\" data-line=\"\">${var}<\/code> as a number using the echo command and returns a negative response otherwise.<\/p>\n<\/div><\/div>\n<p><img decoding=\"async\" class=\"aligncenter wp-image-15021 size-full\" src=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/3.-Check-if-a-Variable-Contains-a-Number-in-Bash.png\" alt=\"output image if variable contains number\" width=\"623\" height=\"287\" srcset=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/3.-Check-if-a-Variable-Contains-a-Number-in-Bash.png 623w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/3.-Check-if-a-Variable-Contains-a-Number-in-Bash-300x138.png 300w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/3.-Check-if-a-Variable-Contains-a-Number-in-Bash-766x353.png 766w\" sizes=\"(max-width: 623px) 100vw, 623px\" \/><\/p>\n<p style=\"text-align: justify;\">As the image depicts above, the script print \u201c23 is a number\u201d based on the user input <strong>23<\/strong>. On the contrary, the script does not acknowledge <strong>2@3 <\/strong>as a number by stating \u201c2@3 is not a number\u201d.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"4_Verify_Whether_Variable_Equals_to_0_in_a_Bash_Script\"><\/span>4. Verify Whether Variable Equals to 0 in a Bash Script<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">Now there might be a situation where you need to check whether the input value is <strong>zero <\/strong>to refrain from taking a further decision. You can check the input value by incorporating the <strong>if statement <\/strong>in your script.<\/p>\n<p style=\"text-align: justify;\">So, check the below script to verify whether a variable equals to 0 in bash:<\/p>\n<pre><code class=\"language-bash\" data-line=\"\">#!\/bin\/bash\n\n# taking user variable using read -p command\nread -p &quot;Enter a number: &quot; var\n\n# Check if the variable equals 0\nif [ &quot;$var&quot; -eq 0 ]; then\n\u00a0\u00a0\u00a0 echo &quot;The input variable is Zero.&quot;\nelse\n\u00a0\u00a0\u00a0 echo &quot;The input variable is not Zero.&quot;\nfi<\/code><\/pre>\n<div class=\"su-box su-box-style-default\" id=\"\" style=\"border-color:#aeb0b3;border-radius:0px;max-width:none\"><div class=\"su-box-title\" style=\"background-color:#E1E3E6;color:#000000;border-top-left-radius:0px;border-top-right-radius:0px\"> EXPLANATION<\/div><div class=\"su-box-content su-u-clearfix su-u-trim\" style=\"border-bottom-left-radius:0px;border-bottom-right-radius:0px\">\n<p>The <code class=\"\" data-line=\"\">if statement<\/code> checks if the value of the variable <strong>var <\/strong>is equal to <strong>0<\/strong> using the <code class=\"\" data-line=\"\">-eq<\/code><strong> operator<\/strong>. If the condition is <strong>true<\/strong>, it will print &#8220;The input variable is Zero.&#8221; to the console. Otherwise, if the condition is <strong>false<\/strong>, it will print &#8220;The input variable is not Zero.&#8221;<\/p>\n<\/div><\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-15022 size-full\" src=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/4.-Verify-Whether-Variable-Equals-to-0-in-a-Bash-Script.png\" alt=\"output image when variable value is zero\" width=\"622\" height=\"288\" srcset=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/4.-Verify-Whether-Variable-Equals-to-0-in-a-Bash-Script.png 622w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/4.-Verify-Whether-Variable-Equals-to-0-in-a-Bash-Script-300x139.png 300w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/4.-Verify-Whether-Variable-Equals-to-0-in-a-Bash-Script-767x355.png 767w\" sizes=\"(max-width: 622px) 100vw, 622px\" \/><\/p>\n<p style=\"text-align: justify;\">Upon the first execution, the input value is <strong>9<\/strong>, therefore the command line returns \u201cThe input variable is not Zero.\u201d whereas in the second case, the command line returns &#8220;The input variable is not Zero.&#8221; provided that the user value is <strong>0<\/strong>.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"5_Check_a_Variable_Contains_Text_String_Rather_Than_Integer_Value\"><\/span>5. Check a Variable Contains Text String Rather Than Integer Value<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">Following the previous example, you can check whether your input value is a specific text string rather than an integer. You can follow the code given below to practice the concept where I take the \u201chello\u201d string to the <strong>you_variable <\/strong>variable and later incorporate the<strong> if statement <\/strong>to check whether it matches the predefined string value.<\/p>\n<p style=\"text-align: justify;\">Now, follow the bash script to check if a variable contains text string rather than integer value:<\/p>\n<pre><code class=\"language-bash\" data-line=\"\">#!\/bin\/bash\n\n# Your variable\nyour_variable=&quot;hello&quot;\n\n# Check if the variable equals &quot;hello&quot;\nif [ &quot;$your_variable&quot; = &quot;hello&quot; ]; then\n\u00a0\u00a0\u00a0 echo &quot;The variable is equal to &#039;hello&#039;.&quot;\nelse\n\u00a0\u00a0\u00a0 echo &quot;The variable is not equal to &#039;hello&#039;.&quot;\nfi<\/code><\/pre>\n<div class=\"su-box su-box-style-default\" id=\"\" style=\"border-color:#aeb0b3;border-radius:0px;max-width:none\"><div class=\"su-box-title\" style=\"background-color:#E1E3E6;color:#000000;border-top-left-radius:0px;border-top-right-radius:0px\"> EXPLANATION<\/div><div class=\"su-box-content su-u-clearfix su-u-trim\" style=\"border-bottom-left-radius:0px;border-bottom-right-radius:0px\">\n<p>The variable your_variable contains a string value \u201chello\u201d. Then the <code class=\"\" data-line=\"\">if<\/code> statement checks if the value of <strong>your_variable <\/strong>is equal to the string &#8220;hello\u201d with the <code class=\"\" data-line=\"\">[ &quot;$your_variable&quot; = &quot;hello&quot; ]<\/code> expression. If the value of <strong>your_variable <\/strong>is &#8220;hello&#8221; the script will print &#8220;The variable is equal to &#8216;hello&#8217;.&#8221; to the console. Otherwise, if the value differs from &#8220;hello&#8221;, it will print &#8220;The variable is not equal to &#8216;hello&#8217;.&#8221;<\/p>\n<\/div><\/div>\n<p style=\"text-align: justify;\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-15023 size-full\" src=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/5.-Check-if-a-Variable-Has-a-Value-in-Bash.png\" alt=\"output image\" width=\"612\" height=\"161\" srcset=\"https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/5.-Check-if-a-Variable-Has-a-Value-in-Bash.png 612w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/5.-Check-if-a-Variable-Has-a-Value-in-Bash-300x79.png 300w, https:\/\/linuxsimply.com\/wp-content\/uploads\/2023\/08\/5.-Check-if-a-Variable-Has-a-Value-in-Bash-768x202.png 768w\" sizes=\"(max-width: 612px) 100vw, 612px\" \/>As the image suggests, the string value \u201chello\u201d matches with the\u00a0 <code class=\"\" data-line=\"\">[ &quot;$your_variable&quot; = &quot;hello&quot; ]<\/code> expression, thus returning \u201cThe variable is equal to \u2018hello\u2019.\u201d in the command line.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Conclusion\"><\/span>Conclusion<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">In this article, I have discussed five different scenarios to check the variable value in the bash script. Of course, there are numerous examples or user-case scenarios you can create if you want. If you have any queries or suggestions related to this article, don\u2019t forget to comment below. I am one click away to engage in a knowledge-sharing conversation with you. Thank You!<\/p>\n<h2><span class=\"ez-toc-section\" id=\"People_Also_Ask\"><\/span>People Also Ask<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<h3><span class=\"ez-toc-section\" id=\"How_to_check_a_variable_value_in_bash\"><\/span>How to check a variable value in bash?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">To check a variable value in bash, you can use the <code class=\"\" data-line=\"\">-z<\/code> operator inside the <code class=\"\" data-line=\"\">if<\/code> conditional statement. Here is the basic syntax: <code class=\"\" data-line=\"\">if [ -z ${variable+x} ]<\/code>. It checks if the variable value is assigned or not.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Does_bash_have_variable_types\"><\/span>Does bash have variable types?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">In Bash, variables are not <strong>explicitly declared <\/strong>with specific types, unlike some other programming languages that have strict typing systems. However,\u00a0 Bash does not have variable types. All variables in Bash are treated as <strong>strings<\/strong>.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"How_to_check_numeric_value_in_Bash\"><\/span>How to check numeric value in Bash?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">You can check if a value is <strong>numeric <\/strong>in Bash using the <code class=\"\" data-line=\"\">[[<\/code> double brackets with the <code class=\"\" data-line=\"\">=~<\/code> operator and a regular expression. For example: <code class=\"\" data-line=\"\">[[ $value =~ ^[0-9]+$ ]]<\/code>. This expression will return <strong>true <\/strong>if <strong>$value <\/strong>contains only <strong>numeric digits<\/strong>, and <strong>false <\/strong>otherwise.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"How_to_read_a_value_in_Bash\"><\/span>How to read a value in Bash?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">To read a value from the user in Bash, you can use the <strong>read command<\/strong>. The syntax is like: <code class=\"\" data-line=\"\">read -p &quot;Enter a value: &quot; variable_name<\/code>. With this command, you will be prompted with the message &#8220;Enter a value: &#8220;, and the input will be stored in the variable named <strong>variable_name<\/strong>.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"How_to_check_string_length_0_in_Bash\"><\/span>How to check string length 0 in Bash?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">To check if a string has a length of <strong>0<\/strong> in <strong>Bash<\/strong>, you can use the following one-liner: <code class=\"\" data-line=\"\">[[ -z &quot;$string&quot; ]]<\/code>. Replace <strong>$string<\/strong> with the <strong>variable<\/strong> or <strong>string<\/strong> you want to check. The <strong>[[ -z &#8220;$string&#8221; ]]<\/strong> expression will evaluate to <strong>true<\/strong> if the string has a length of <strong>0 <\/strong>(<strong>empty<\/strong>), and <strong>false<\/strong> otherwise.<\/p>\n<p><script type=\"application\/ld+json\">\n{\n  \"@context\": \"https:\/\/schema.org\",\n  \"@type\": \"FAQPage\",\n  \"mainEntity\": [{\n    \"@type\": \"Question\",\n    \"name\": \"How to check a variable value in bash?\",\n    \"acceptedAnswer\": {\n      \"@type\": \"Answer\",\n      \"text\": \"To check a variable value in bash, you can use the -z operator inside the if conditional statement. Here is the basic syntax: if [ -z ${variable+x} ]. 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This expression will return true if $value contains only numeric digits, and false otherwise.\"\n    }\n  },{\n    \"@type\": \"Question\",\n    \"name\": \"How to read a value in Bash?\",\n    \"acceptedAnswer\": {\n      \"@type\": \"Answer\",\n      \"text\": \"To read a value from the user in Bash, you can use the read command. The syntax is like: read -p \\\"Enter a value: \\\" variable_name. With this command, you will be prompted with the message \\\"Enter a value: \\\", and the input will be stored in the variable named variable_name.\"\n    }\n  },{\n    \"@type\": \"Question\",\n    \"name\": \"How to check string length 0 in Bash?\",\n    \"acceptedAnswer\": {\n      \"@type\": \"Answer\",\n      \"text\": \"To check if a string has a length of 0 in Bash, you can use the following one-liner: [[ -z \\\"$string\\\" ]]. Replace $string with the variable or string you want to check. The [[ -z \\\"$string\\\" ]] expression will evaluate to true if the string has a length of 0 (empty), and false otherwise.\"\n    }\n  }]\n}\n<\/script><br \/>\n<span style=\"font-size: 18pt; color: #003366;\"><strong>Related Articles<\/strong><\/span><\/p>\n<ul>\n<li><strong><a class=\"in-cell-link\" href=\"https:\/\/linuxsimply.com\/bash-scripting-tutorial\/variables\/declaration-and-assignment\/declare-variable\/\" target=\"_blank\" rel=\"noopener\">How to Declare Variable in Bash Scripts? 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