Awk length of word

In this article, we are going to see how to get string length in Bash scripting.

Here are a few ways from which we can get the length of the string in BASH:

1. Using the # operator
2. Using while loop
3. Using expr command
4. Using awk command
5. Using wc command

Using these mentioned tools and commands, we will be able to get the length of a string variable in the BASH script.

Method 1: Using the # operator

#!usr/bin/env bash
str="this is a string"
n=${#str}
echo "Length of the string is : $n "

We can use the # operator to get the length of the string in BASH, we need to enclose the variable name enclosed in “{ }” and inside of that, we use the # to get the length of the string variable. Thus, using the “#” operator in BASH, we can get the length of the string variable.

Method 2: Using while loop

In this example. we can use the while loop along with the read command to obtain the length of the string. Firstly we initialize the string to whatever you like, it can be a user input, positional parameter, etc. It’s quite easy to work with the variable, so therefore we create a variable for the string and also initialize the length “n” to 0. Then we start the while loop by reading characters by character using the argument -n1 i.e read just the single character from the entire string. 

For every character in the variable “str” i.e. after every iteration, we increment the length “n” by one. In the while loop, we are reading from the string “str” with echo command along with -n argument which restricts to escape of the newline character. Thus at the end of the loop, we have the length of the string in the variable n which can be accessed as per requirements. 

#!usr/bin/env bash

str="this is a string"
n=0
while read -n1 character; do
    n=$((n+1)); 
done < <(echo -n "$str")
echo "Length of the string is : $n "

Method 3: Using expr command

#!usr/bin/env bash

str="Test String@#$"
n=`expr "$str" : '.*'`
echo "Length of the string is : $n "

In this example, we are using the expr command to find the length of the string in BASH. The expr command takes the first argument as the string variable and then the comparison operator “:” that counts the number of common characters in the string and the next string provided after the “:” operator.  For calculating the length of the string, we parse the previous string. For that “.*” is the regex that gets 0 or more characters of the previously provided token. Even parsing the string instead of “.*” will work

n=`expr "$str" : "$str"`

Here we have used the backticks(“` `“) but even using the $( ) there is no such advantage of using the former over the latter. Both serve the same purpose but the $( ) nests very effective than the backticks. 

#!usr/bin/env bash

str="Test String@#$"
n=`expr length "$str"`
echo "Length of the string is : $n "

We can even use the built-in function in expr command “length” that gets the length of the string as a parameter just after the function. The length command as the name suggests gives us the length of the provided string or any variable. 

Remember for every code snippet following this one, you can use the $( ) instead of backticks(` `). 

n=$(expr length "$str")

Method 4: Using awk command

#!usr/bin/env bash

str="this is a string"
n=`echo $str | awk '{print length}'`
echo "Length of the string is : $n "

We can even use the awk command to get the length of the string. We use the function length which is built-in awk along with print that prints the value and thus stores the length of the string after piping (“|“) with the echo command. 

In the expression, echo $str | awk ‘{print length}’ we echo the string variable “str” and then redirect (pipe) the output of it to the awk command. In the awk command, we print the output of the length function, which takes the str variable and stores it in the variable “n“.

Method 5: Using wc command

#!usr/bin/env bash

str="this is a string"
n=`echo -n "$str"|wc -c`
echo "Length of the string is : $n "

In this demonstration, we have used the wc command to get the length of the string. Inside of this command, “echo -n “$str” | wc -c” the echo command is given an argument -n which doesn’t escape the new line character. Next, the output of the echo command is redirected (piped) to the wc command which again is given the argument -c which counts the number of bytes in the provided variable, we can even use -m which also precisely counts the number of characters.   

echo -n "$str" | wc -m

Example

Returns the number of characters of the given String

Considerations

• If a number is given instead a String, the result will be the length of the String representing the given number. I.e. If we execute length(12345) the result will be the same as length("12345"), that is 5

• If no value is given, the result will be the length of the actual row being processed, that is length($0)

• It can be used inside a pattern or inside code-blocks.

Examples

Here are a few examples demonstrating how length()works

$ cat file
AAAAA
BBBB
CCCC
DDDD
EEEE

---

Inside a pattern

Filter all lines with a length bigger than 4 characters

$ awk ' length($0) > 4 ' file
AAAAA

---

Inside a code block

Will print the size of the current line

$ awk '{ print length($0) }' file
5
4
4
4
4

---

With no data given

Will print the size of the current line

$ awk '{ print length }' file
5
4
4
4
4

Will print the size of the current line

$ awk '{ print length() }' file
5
4
4
4
4

---

Number given instead of String

Will print the size of the String representing the number

$ awk '{ print length(12345) }' file
5
5
5
5
5

---

Fixed String given

Will print the size of the String

$ awk '{ print length("12345") }' file
5
5
5
5
5

---

AWK has the following built-in String functions −

asort(arr [, d [, how] ])

This function sorts the contents of arr using GAWK’s normal rules for comparing values, and replaces the indexes of the sorted values arr with sequential integers starting with 1.

Example

[jerry]$ awk 'BEGIN {
   arr[0] = "Three"
   arr[1] = "One"
   arr[2] = "Two"
   print "Array elements before sorting:"
   
   for (i in arr) {
      print arr[i]
   }
   asort(arr)
   print "Array elements after sorting:"
   
   for (i in arr) {
      print arr[i]
   }
}'

On executing this code, you get the following result −

Output

Array elements before sorting:
Three
One
Two
Array elements after sorting:
One
Three
Two

asorti(arr [, d [, how] ])

The behavior of this function is the same as that of asort(), except that the array indexes are used for sorting.

Example

[jerry]$ awk 'BEGIN {
   arr["Two"] = 1
   arr["One"] = 2
   arr["Three"] = 3
   asorti(arr)
   print "Array indices after sorting:"
   
   for (i in arr) {
      print arr[i]
   }
}'

On executing this code, you get the following result −

Output

Array indices after sorting:
One
Three
Two

gsub(regex, sub, string)

gsub stands for global substitution. It replaces every occurrence of regex with the given string (sub). The third parameter is optional. If it is omitted, then $0 is used.

Example

[jerry]$ awk 'BEGIN {
   str = "Hello, World"
   print "String before replacement = " str
   
   gsub("World", "Jerry", str)
   print "String after replacement = " str
}'

On executing this code, you get the following result −

Output

String before replacement = Hello, World
String after replacement = Hello, Jerry

index(str, sub)

It checks whether sub is a substring of str or not. On success, it returns the position where sub starts; otherwise it returns 0. The first character of str is at position 1.

Example

[jerry]$ awk 'BEGIN {
   str = "One Two Three"
   subs = "Two"
   ret = index(str, subs)
   
   printf "Substring "%s" found at %d location.n", subs, ret
}'

On executing this code, you get the following result −

Output

Substring "Two" found at 5 location.

length(str)

It returns the length of a string.

Example

[jerry]$ awk 'BEGIN {
   str = "Hello, World !!!"
   print "Length = ", length(str)
}'

On executing this code, you get the following result −

Length = 16

match(str, regex)

It returns the index of the first longest match of regex in string str. It returns 0 if no match found.

Example

[jerry]$ awk 'BEGIN {
   str = "One Two Three"
   subs = "Two"
   ret = match(str, subs)
  
   printf "Substring "%s" found at %d location.n", subs, ret
}'

On executing this code, you get the following result −

Output

Substring "Two" found at 5 location

split(str, arr, regex)

This function splits the string str into fields by regular expression regex and the fields are loaded into the array arr. If regex is omitted, then FS is used.

Example

[jerry]$ awk 'BEGIN {
   str = "One,Two,Three,Four"
   split(str, arr, ",")
   print "Array contains following values"
   
   for (i in arr) {
      print arr[i]
   }
}'

On executing this code, you get the following result −

Output

Array contains following values
One
Two
Three
Four

printf(format, expr-list)

This function returns a string constructed from expr-list according to format.

Example

[jerry]$ awk 'BEGIN {
   param = 1024.0
   result = sqrt(param)
   
   printf "sqrt(%f) = %fn", param, result
}'

On executing this code, you get the following result −

Output

sqrt(1024.000000) = 32.000000

strtonum(str)

This function examines str and return its numeric value. If str begins with a leading 0, it is treated as an octal number. If str begins with a leading 0x or 0X, it is taken as a hexadecimal number. Otherwise, assume it is a decimal number.

Example

[jerry]$ awk 'BEGIN {
   print "Decimal num = " strtonum("123")
   print "Octal num = " strtonum("0123")
   print "Hexadecimal num = " strtonum("0x123")
}'

On executing this code, you get the following result −

Output

Decimal num = 123
Octal num = 83
Hexadecimal num = 291

sub(regex, sub, string)

This function performs a single substitution. It replaces the first occurrence of the regex pattern with the given string (sub). The third parameter is optional. If it is omitted, $0 is used.

Example

[jerry]$ awk 'BEGIN {
   str = "Hello, World"
   print "String before replacement = " str
   
   sub("World", "Jerry", str)
   print "String after replacement = " str
}'

On executing this code, you get the following result −

Output

String before replacement = Hello, World
String after replacement = Hello, Jerry

substr(str, start, l)

This function returns the substring of string str, starting at index start of length l. If length is omitted, the suffix of str starting at index start is returned.

Example

[jerry]$ awk 'BEGIN {
   str = "Hello, World !!!"
   subs = substr(str, 1, 5)

   print "Substring = " subs
}'

On executing this code, you get the following result −

Output

Substring = Hello

tolower(str)

This function returns a copy of string str with all upper-case characters converted to lower-case.

Example

[jerry]$ awk 'BEGIN {
   str = "HELLO, WORLD !!!"
   print "Lowercase string = " tolower(str)
}'

On executing this code, you get the following result −

Output

Lowercase string = hello, world !!!

toupper(str)

This function returns a copy of string str with all lower-case characters converted to upper case.

Example

[jerry]$ awk 'BEGIN {
   str = "hello, world !!!"
   print "Uppercase string = " toupper(str)
}'

On executing this code, you get the following result −

Output

Uppercase string = HELLO, WORLD !!!

awk_built_in_functions.htm