Bash Script to Count Characters in a File

Use the command wc -m filename in Bash to count the number of characters in a file, or use a script with char_count=$(wc -m < filename) to store the count.

Examples

Inputfile.txt content: Hello

Output6

Inputfile.txt content: Hello World!

Output12

Inputfile.txt content: (empty file)

Output0

How to Think About It

To count characters in a file, think of reading the file's content and measuring how many characters it contains, including spaces and newlines. Bash provides a simple tool wc -m that counts characters directly, so the script just needs to run this command and capture its output.

Algorithm

1

Get the filename as input.

2

Use the command to count characters in the file.

3

Store or print the character count.

Code

bash

#!/bin/bash

filename="$1"

if [[ ! -f "$filename" ]]; then
  echo "File not found!"
  exit 1
fi

char_count=$(wc -m < "$filename")
echo "Number of characters in '$filename': $char_count"

Output

Number of characters in 'file.txt': 12

Dry Run

Let's trace counting characters in a file containing 'Hello World!'

1

Check file existence

filename='file.txt' exists

2

Count characters

wc -m < file.txt returns '12'

3

Print result

Output: Number of characters in 'file.txt': 12

Step	Action	Value
1	Check file	file.txt exists
2	Count characters	12
3	Print output	Number of characters in 'file.txt': 12

Why This Works

Step 1: Use wc -m to count characters

The wc -m command counts all characters in the file, including spaces and newlines.

Step 2: Redirect file content to wc

Using < filename sends the file content to wc without printing the filename.

Step 3: Store and print the count

The script saves the count in a variable and prints it with a clear message.

Alternative Approaches

Using awk

bash

awk '{ total += length($0) + 1 } END { print total }' filename

Counts characters including newline per line; may differ if file does not end with newline.

Using Perl

bash

perl -lne 'END { print $. ? $. + length($_) : 0 }' filename

More complex but flexible for character counting with custom rules.

Complexity: O(n) time, O(1) space

Time Complexity

The command reads each character once, so time grows linearly with file size.

Space Complexity

No extra memory is needed beyond a few variables; counting is done on the fly.

Which Approach is Fastest?

wc -m is optimized and fastest; alternatives like awk or perl are slower but offer flexibility.

Approach	Time	Space	Best For
wc -m	O(n)	O(1)	Simple, fast character count
awk	O(n)	O(1)	Custom line-based counting
perl	O(n)	O(1)	Flexible, complex counting