Shell Scripting – Here Strings
Here String is a kind of string that is used for input redirection from text or a variable. In here string Input will be mentioned in the same line within the quotes. the string inside the quotes is known as the Here string and Its command contains “<<<” (3 less than the symbol). Here string and a heredoc are extremely similar, but the former is a lot more simplified version of the latter.
Because of this, a delimiter token is not required in this text. Whenever we need a quick technique to transform some strings into a command, it is typically preferred. It is also known as an ordinary string which is used for the purpose of input redirection, It’s not a special kind of string. The execution contains only a few steps.
Basic Syntax:
To construct a here-string, we use the “<<<” operator to redirect a string into a command. Concretely, the syntax is:
$ command <<< $DATA
What it essentially does is expand the variable DATA and redirect the output string to the COMMAND.
Usage of Here Strings
For input redirection from text or a variable, the here-string is utilized. On the same line, input is mentioned in single quotations (“).
Example 1: Basic Usage
#!/bin/bash wc -w <<< 'Hello GeeksforGeeks\n'
In this example, the string It is “Hello GeeksforGeeks\n” is called the here-string.
Output:
2
There are 2 words, so the output is been retrieved as 2.
Example 2: String with more words
#!/bin/bash wc -w <<< 'Welcome to GFG a helping platform for CS Students'
In this example, the string “Welcome to GFG a helping platform for CS Students” is called the here-string.
Output:
9
There are 9 words, so the output is been retrieved as 9.
Example 3: Here String with Parameter
if grep -q "txt" <<< "$VAR" then echo "$VAR contains the substring sequence \"txt\"" fi
In the above example, the here-string is present with a parameter $VAR which is working as a parameter.
Example 4: Escape Special Characters in Here String
word=$'HELLO\ngfg' echo "$WORD"
It’s a kind of special character which is sometimes used in the here-string
The above example is here-string with Escape Special Characters and it’s Escaping some characters.
