Differences

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--- soft:bash [2020/09/20 10:11] – Ce Zhang
+++ soft:bash [2021/06/26 05:24] (current) – Ce Zhang
@@ Line 1: / Line 1: @@
+==== a string containinng character ====
+<code>
+if echo "${word}" | grep '[0-9]' >/dev/null; then
+    echo 'Invalid input'
+fi
+string='My string';
+if [[ $string =~ "My" ]]; then
+   echo "It's there!"
+fi
+string='My long string'
+if [[ $string == *"My long"* ]]; then
+  echo "It's there!"
+fi
+[[ ! $VAR =~ [0-9] ]];
+# contains only alphabets and numbers
+$VAR =~ ^[[:alnum:]]+$
+# Or
+$VAR =~ ^[0-9a-zA-Z]+$
+#!/bin/bash
+while true; do
+   read -r -p "Enter a string: " VAR
+   if [[ $VAR =~ ^[[:alnum:]]+$ ]];then
+      echo "OK: Contains alphabets and numbers"
+   else
+      echo "NOK: Contains special character"
+   fi
+done
+#!/bin/bash
+while true; do
+   read -r -p "Enter a string: " VAR
+   if [[ $VAR =~ ^[0-9]+$ ]];then
+      echo "Input contains number"
+   else
+      echo "Input contains non numerical value"
+   fi
+done
+</code>
+reference:
+  - [[https://www.golinuxcloud.com/check-if-string-contains-numbers-shell-script/#5_Check_if_string_contains_special_characters| link1]]
+  - [[https://ryanstutorials.net/bash-scripting-tutorial/bash-if-statements.php|if statement]]
+==== date command in bash ====
+[[https://linuxhint.com/date-command-bash/|reference]]
+<code>
+#!/bin/bash
+today = `date +%m-%d-%Y`
+echo $today
+</code>
+==== Replace String in a File with the `sed` Command ====
+<code>
+sed -i 's/search_string/replace_string/' filename
+</code>
 ==== Control and comparison====
 <code>