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    <p>You wrote:</p> <pre><code>if ["$var_check"=="c"];then </code></pre> <p>The <code>[</code> command is a command; its name must be surrounded by spaces (put simplistically).</p> <pre><code>if [ "$var_check" == "c" ]; then </code></pre> <p>The last argument, <code>]</code>, must also be preceded by a space. The operands within must also be space separated; they need to be separate arguments. The rules for the <code>[[ ... ]]</code> operator are a bit different, but using spaces helps people read the code even there. What you wrote is a bit like expecting:</p> <pre><code>ls"-l"/dev/tty </code></pre> <p>to work; it won't.</p> <p>You also need to double check whether your <code>test</code> or <code>[</code> operator supports <code>==</code>; the normal form is <code>=</code>.</p> <hr> <p>The line:</p> <pre><code>var_check= echo $str |awk -F . '{if (NF&gt;1) {print $NF}}' </code></pre> <p>This runs the <code>echo</code> command with <code>var_check</code> set as an environment variable, which is unlikely to be what you wanted. You almost certainly intended to write:</p> <pre><code>var_check=$(echo $str |awk -F . '{if (NF&gt;1) {print $NF}}') </code></pre> <p>This runs the <code>echo</code> and <code>awk</code> commands and captures the output in <code>var_check</code>. Use the <code>$(...)</code> notation in preference to the older but more complex to use <code>`...`</code> notation. In simple cases, they look the same; when you nest them, the <code>$(...)</code> notation is far, far simpler to understand and use.</p> <p>Also, looking on the larger scale (3 lines instead of just 1 line):</p> <pre><code>echo "enter file name" read num var_check=$(echo $str |awk -F . '{if (NF&gt;1) {print $NF}}') </code></pre> <p>You read the file name into variable <code>num</code>; you then echo <code>$str</code> instead of <code>$num</code>. If you've already got <code>$str</code> set somewhere earlier in the script (in unshown code), what you've got may be fine. Taken as a standalone fragment, it isn't right.</p> <p>You could also simplify the <code>awk</code> a little:</p> <pre><code>var_check=$(echo $str |awk -F . 'NF &gt; 1 {print $NF}') </code></pre> <p>This would work the same as what you wrote, but uses fewer parentheses and braces.</p>
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    1. USJonathan Leffler
    1. USJonathan Leffler
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      1. USkrishna
 

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