Bash For Loop – Syntax and Examples

Bash For Loop

Bash For loop is a statement that lets you repeat a set of Bash commands over a list of values. The list may contain words, filenames, numbers, array elements, command output, or generated sequences.

Use a Bash for loop when the number of items is already known or can be generated before the loop starts. For example, it is useful for processing files in a directory, printing array values, running the same command for several users, or repeating commands for a range of numbers.

Bash For Loop Syntax for Lists, Arrays, and Counters

The most common Bash for loop syntax is:

for variable in item1 item2 item3
do
    command1
    command2
done

You can also write the same loop on one line by using semicolons. This form is often used directly in the terminal.

for variable in item1 item2 item3; do command; done

The variable receives one item at a time. The commands between do and done run once for each item.

In this tutorial, we will go through following topics.

• Example – Iterate over elements of an Array
• Example – Consider white spaces in String as word separators
• Example – Consider each line in string as a separate word
• Example – Iterate over a Sequence
• Example – Using a counter
• Example – With break command
• Example – Skip one iteration with continue
• Example – Loop over files that match a pattern

Bash For Loop – Iterate over Elements of Array

The syntax to loop or iterate over elements of an array using Bash For loop is

#!/bin/bash

arr=( "element1" "element2" . . "elementN" )

for i in "${arr[@]}"
do
	echo $i
	#statement(s)
done

For each element in arr the statements from do till done are executed, and each element could be accessed as i within the for loop for respective iteration.

Keep the array expansion inside double quotes as "${arr[@]}". This preserves array elements that contain spaces, such as "shell script", as one value.

Bash For Loop Example

In this For loop example, we will take an array of three strings, and iterate over the elements of array.

Bash Script File

#!/bin/bash

# declare an array
arr=( "bash" "shell" "script" )

# for loop that iterates over each element in arr
for i in "${arr[@]}"
do
    echo $i
done

When the above bash for loop example is run in Terminal, you will get the following output.

Output

~$ ./bash-for-loop-example-4
bash
shell
script

Bash For Loop – Whitespaces in String as Word Separators

The syntax of Bash For loop to consider whitespaces in given string as word separators is

#!/bin/bash

for word in $str;
do
	#statement(s)
done

str is a string

for each word in str the statements from do till done are executed, and word could be accessed within the for loop for respective iteration.

This form intentionally leaves $str unquoted, so Bash performs word splitting. It is useful only when you really want spaces, tabs, and newlines to split the string into separate words. If the string contains filenames or values with spaces, use an array instead.

Example

In the following example, we will take a string with words separated by white spaces, and iterate over the words using for loop.

Bash Script File

#!/bin/bash

str="this example 
demonstrates the for loop
that considers all white-space
characters as word separators"

## now loop through the above array
for i in $str;
do
   echo "$i"	
done

When the above bash for loop example is run in Terminal, you will get the following output.

Output

~$ ./bash-for-loop-example
this
example
demonstrates
the
for
loop
that
considers
all
white-space
characters
as
word
separators

Bash For Loop – Each Line in String as Element

The syntax of Bash For Loop to consider each line in string as element is

#!/bin/bash

for line in "$str";
do
	#statement(s)
done

str is a string

for each line that is a line in str, statements from do till done are executed, and line could be accessed within the for loop for respective iteration.

Note: Observe that the only difference between first type of for loop and this one is the double quotes around string variable.

When "$str" is quoted, Bash treats the whole string as one item. The embedded newline characters are preserved when the variable is printed, so the output appears on multiple lines. If you need a separate loop iteration for every line, use the line-reading example shown after the existing example.

Example

In the following example, we will take a string with four lines. We will use for loop to iterate over the elements in string separated by new line.

Bash Script File

#!/bin/bash

str="this example 
demonstrates the for loop
that considers new line
characters as line separators"


## loop through each line in above string
for line in "$str"
do
   echo "$line"	
done

When the above bash for loop example is run in Terminal, we will get the following output.

Output

~$ ./bash-for-loop-example-2
this example 
demonstrates the for loop
that considers new line
characters as word separators

Bash Script to Process Each Line as a Separate Iteration

For line-by-line processing, a while read loop is more reliable than a for loop because it preserves spaces in each line.

#!/bin/bash

str="first line
second line
third line"

while IFS= read -r line
do
    echo "Line: $line"
done <<< "$str"

Bash For Loop – Iterate Over a Sequence

The syntax of Bash For loop to iterate over a sequence of numbers is

#!/bin/bash

for i in `seq m n`;
do
	#statement(s)
done

for loop is iterated for each element i in the sequence from m to n . The element in the sequence, <span style="font-family: Courier 10 Pitch, Courier, monospace;"><span style="font-size: 12.8px; background-color: #d2eeca;">i</span></span>  is accessible during the iteration.

In Bash, brace expansion is another common way to loop over a fixed range of numbers.

for i in {1..5}
do
    echo "$i"
done

Brace expansion is expanded before the loop runs. Use seq when the range values are calculated at runtime or stored in variables.

Example

In the following Bash Script, we will use For Loop to iterate over a sequence of numbers.

Bash Script File

#!/bin/bash

for i in `seq 1 10`;
do
	echo $i
done

When the above bash for loop example is run in Terminal, you will get the following in the output.

Output

~$ ./bash-for-loop-example-3
1
2
3
4
5
6
7
8
9
10

Bash For Loop – Use Counter to Iterate Over Elements of Array

The syntax of Bash For Loop to use a variable for counter to iterate over elements of an array is

#!/bin/bash

array=( "element1" "element2" . . "elementN" )

arraylength=${#array[@]}

for (( i=1; i<${arraylength}+1; i++ ));
do
	echo $i : " ${array[$i-1]}
	#statement(s)
done

Length of an array could be calculated using ${#array[@]} and the the statements from do till done are could iterated based on a condition. The syntax of for loop might look similar to that of Java For Loop.

A counter loop is useful when you need both the index and the value. Bash array indexes start at 0, but the example below prints a human-friendly count starting from 1.

Example

In the following Bash Script, we will use For Loop to iterate over an Array using a counter variable.

Bash Script File

#!/bin/bash

#array variable
arr=( "bash" "shell" "script" )

# get length of an array to a variable
arrlength=${#arr[@]}

# for loop to read all values and indexes
for (( i=1; i<${arrlength}+1; i++ ));
do
  echo $i " : " ${arr[$i-1]}
done

When the above bash for loop example is run in Terminal, we will get the following output.

Output

~$ ./bash-for-loop-example-5
1  :  bash
2  :  shell
3  :  script

Bash For Loop – Break Command

The syntax of For Loop with break command, to break the for loop abruptly even before the for condition fails is

#!/bin/bash

array=( "element1" "element2" . . "elementN" )

for i in "${array[@]}"
do
	#statement(s)

	if [ BREAKING_CONDITION ]; then
		break
	fi
done

BREAKING_CONDITION decides when to break the for loop prematurely. When the breaking condition evaluates to TRUE, then break statement is executed. break command breaks the loop that is immediate to the break statement.

Example

In the following Bash Script, we will write a For Loop containing break statement. The break statement is surrounded in an if statement, which executes the body when the element is “script”. In other words, we are breaking the for loop if the element is “script”.

Bash Script File

#!/bin/bash

# declare an array
arr=( "bash" "shell" "script" "language" )

# for loop that iterates over each element in arr
for i in "${arr[@]}"
do
    echo $i
    # break for loop based on a condition
    if [ $i == "script" ]; then
        break
    fi
done

When the above bash for loop example is run in Terminal, we will get the following output.

Output

~$ ./bash-for-loop-example-6 
bash
shell
script

Bash For Loop – Continue Command to Skip an Item

The continue command skips the remaining commands in the current iteration and moves the loop to the next item. It is useful when one value should be ignored, but the loop should not stop completely.

#!/bin/bash

arr=( "bash" "skip" "shell" "script" )

for item in "${arr[@]}"
do
    if [ "$item" = "skip" ]; then
        continue
    fi

    echo "$item"
done

In this example, the value skip is not printed, but the loop continues with the remaining array elements.

bash
shell
script

Bash For Loop – Loop Over Files Matching a Pattern

A Bash for loop is often used with filename patterns. The following script prints the names of all .txt files in the current directory.

#!/bin/bash

for file in *.txt
do
    echo "Text file: $file"
done

When looping over files, quote the variable as "$file" inside commands. This prevents filenames with spaces from being split into multiple arguments.

#!/bin/bash

for file in *.txt
do
    cp "$file" "backup/$file"
done

Bash For Loop Forms and When to Use Them

Bash for loop form	Best used for	Example pattern
for item in list	Words, array values, filenames, command output	for name in Alice Bob
for item in "${array[@]}"	Array elements, including values with spaces	for item in "${arr[@]}"
for i in {1..10}	Fixed numeric ranges	for i in {1..10}
for i in `seq 1 10`	Numeric ranges generated by a command	for i in `seq $start $end`
for (( ... ))	Counter-based loops with arithmetic conditions	for (( i=0; i<5; i++ ))

Common Bash For Loop Mistakes

• Forgetting do or done: Every multi-line Bash for loop needs both keywords.
• Using unquoted variables inside commands: Use "$file" or "$item" when the value may contain spaces.
• Expecting quoted strings to split into words: "$str" is one item; $str is split by whitespace.
• Using a for loop for line-by-line file reading: Prefer while IFS= read -r line for reading files or multiline text safely.
• Assuming file patterns always match: If no file matches *.txt, Bash may keep the literal pattern depending on shell options.

FAQs on Bash For Loop Syntax and Examples

Editorial QA Checklist for Bash For Loop Tutorials

• Check that each Bash for loop has matching for, do, and done keywords.
• Confirm that array examples use "${array[@]}" when preserving elements is important.
• Verify that output blocks match the shown Bash script examples.
• Make sure line-by-line processing is not confused with whitespace-based word splitting.
• Review whether each new code block uses the correct PrismJS class, such as language-bash, language-bash syntax, or output.

Conclusion

In this Bash Tutorial – Bash For Loop, we have learnt to iterate specific set of statements over words, lines in a string, elements in a sequence or elements in an array with the help of Bash Script examples. We also covered counter loops, break, continue, file patterns, and common quoting mistakes that affect Bash loop behavior.