Loops in Bash

Posted on Dec 03, 2019 in Computer Science

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Fish Shell is preferred to Bash/Zsh. The following content is for Bash/Zsh only.

Tips and Traps

  1. Forggeting $ is a common mistake when using a shell variable.
In [2]:
%%bash

for x in 1 2 3 4 5; do
	echo $x
done

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5
In [5]:
%%bash

for x in {1..5}; do
	echo $x
done

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4
5
In [6]:
%%bash

for x in {1..5..2}; do
	echo $x
done

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5
In [9]:
%%bash

for x in $(seq 1 2 5); do
    echo $x
done

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3
5
In [11]:
%%bash

for (( i=1; i<=5; i++ )); do  
   echo $i
done

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5
In [12]:
%%bash

for (( i=1; i<=5; ++i )); do  
   echo $i
done

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5

Below is an infinite loop.

In [12]:
%%bash

for (( ; ; )); do  
   echo "This is a infinite loop!"
done

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In [4]:
%%bash

for dir in $(ls -d */); do
    echo $dir
done

f2.csv/
spark-warehouse/

break and continue

break, continue and exit work as in other programming languages.

Reference

https://www.cyberciti.biz/faq/bash-for-loop/

In [ ]:

programming Bash loop