{"id":5403,"date":"2023-02-15T14:00:51","date_gmt":"2023-02-15T08:30:51","guid":{"rendered":"https:\/\/trysiteprice.com\/blog\/?p=5403"},"modified":"2023-02-15T14:00:51","modified_gmt":"2023-02-15T08:30:51","slug":"bash-shell-trim-leading-white-space-from-input-variables","status":"publish","type":"post","link":"https:\/\/trysiteprice.com\/blog\/bash-shell-trim-leading-white-space-from-input-variables\/","title":{"rendered":"Bash Shell: Trim Leading White Space From Input Variables"},"content":{"rendered":"<p>In Bash, you can use parameter expansion to trim leading white space from input variables. Here&#8217;s an example:<\/p>\n<div class=\"bg-black mb-4 rounded-md\">\n<div class=\"flex items-center relative text-gray-200 bg-gray-800 px-4 py-2 text-xs font-sans\"><\/div>\n<div class=\"p-4 overflow-y-auto\"><code class=\"!whitespace-pre hljs language-bash\"><span class=\"hljs-meta\">#!\/bin\/bash<\/span><\/p>\n<p>input=<span class=\"hljs-string\">\"   hello world\"<\/span><br \/>\ntrimmed=<span class=\"hljs-variable\">${input#\"${input%%[![:space:]]*}\"}<\/span><br \/>\n<span class=\"hljs-built_in\">echo<\/span> <span class=\"hljs-string\">\"Original input: \\\"<span class=\"hljs-variable\">$input<\/span>\\\"\"<\/span><br \/>\n<span class=\"hljs-built_in\">echo<\/span> <span class=\"hljs-string\">\"Trimmed input: \\\"<span class=\"hljs-variable\">$trimmed<\/span>\\\"\"<\/span><br \/>\n<\/code><\/div>\n<\/div>\n<p>In this example, the <code>input<\/code> variable is assigned a value with leading white space. The <code>trimmed<\/code> variable uses parameter expansion to remove the leading white space. Here&#8217;s how the parameter expansion works:<\/p>\n<ul>\n<li><code>${input%%[![:space:]]*}<\/code> expands to the longest leading substring of <code>input<\/code> that does not contain any non-white space characters. This effectively removes all leading white space from the input variable.<\/li>\n<li><code>\"${input%%[![:space:]]*}\"<\/code> is used to surround the expression and create a string with the trimmed value.<\/li>\n<li><code>${input#\"${input%%[![:space:]]*}\"}<\/code> expands to the value of <code>input<\/code> with the trimmed value removed from the beginning. This effectively removes the leading white space from the input variable.<\/li>\n<\/ul>\n<p>After running the script, the output should be:<\/p>\n<div class=\"bg-black mb-4 rounded-md\">\n<div class=\"flex items-center relative text-gray-200 bg-gray-800 px-4 py-2 text-xs font-sans\"><\/div>\n<div class=\"p-4 overflow-y-auto\"><code class=\"!whitespace-pre hljs language-python\">Original <span class=\"hljs-built_in\">input<\/span>: <span class=\"hljs-string\">\"   hello world\"<\/span><br \/>\nTrimmed <span class=\"hljs-built_in\">input<\/span>: <span class=\"hljs-string\">\"hello world\"<\/span><br \/>\n<\/code><\/div>\n<\/div>\n<p>Note that this approach only trims leading white space from the input variable. If you also need to trim trailing white space or white space in the middle of the string, you can use similar parameter expansion techniques.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In Bash, you can use parameter expansion to trim leading white space from input variables. Here&#8217;s an example: #!\/bin\/bash input=&#8221; hello world&#8221; trimmed=${input#&#8221;${input%%[![:space:]]*}&#8221;} echo &#8220;Original input: \\&#8221;$input\\&#8221;&#8221; echo &#8220;Trimmed input: \\&#8221;$trimmed\\&#8221;&#8221; In this example, the input variable is assigned a value with leading white space. The trimmed variable uses parameter expansion to remove the leading &#8230; <a title=\"Bash Shell: Trim Leading White Space From Input Variables\" class=\"read-more\" href=\"https:\/\/trysiteprice.com\/blog\/bash-shell-trim-leading-white-space-from-input-variables\/\" aria-label=\"Read more about Bash Shell: Trim Leading White Space From Input Variables\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-5403","post","type-post","status-publish","format-standard","hentry","category-best-tutorial"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.9 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Bash Shell: Trim Leading White Space From Input Variables - TrySitePrice<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/trysiteprice.com\/blog\/bash-shell-trim-leading-white-space-from-input-variables\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Bash Shell: Trim Leading White Space From Input Variables - TrySitePrice\" \/>\n<meta property=\"og:description\" content=\"In Bash, you can use parameter expansion to trim leading white space from input variables. Here&#8217;s an example: #!\/bin\/bash input=&quot; hello world&quot; trimmed=${input#&quot;${input%%[![:space:]]*}&quot;} echo &quot;Original input: &quot;$input&quot;&quot; echo &quot;Trimmed input: &quot;$trimmed&quot;&quot; In this example, the input variable is assigned a value with leading white space. The trimmed variable uses parameter expansion to remove the leading ... 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Here&#8217;s an example: #!\/bin\/bash input=\" hello world\" trimmed=${input#\"${input%%[![:space:]]*}\"} echo \"Original input: \"$input\"\" echo \"Trimmed input: \"$trimmed\"\" In this example, the input variable is assigned a value with leading white space. The trimmed variable uses parameter expansion to remove the leading ... 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