[Linux 常見問題] Check whether a certain file type/extension exists in directory

Source From Here 
Question 
How would you go about telling whether files of a specific extension are present in a directory, with bash? 

How-To 
Consider below shell script: 
- test.sh 

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1. #!/bin/sh  
2. EXT=$1  
3. count=`ls -1 test/*.$EXT 2>/dev/null | wc -l`  
4. if [ $count -ge 1 ]; then  
5.     echo "Folder test contains file with extension '$EXT'"  
6. else  
7.     echo "Folder test contains no file with extension '$EXT'"  
8. fi  

Then you can use it this way: 

# ls test/ // Check the files under folder test
abc.txt def.txt output.log test.log
# ./test.sh log // Check if the folder test contains file with extension as 'log'
Folder test contains file with extension 'log'
# ./test.sh txt // Check if the folder test contains file with extension as 'txt'
Folder test contains file with extension 'txt'
# ./test.sh exe // Check if the folder test contains file with extension as 'exe'
Folder test contains no file with extension 'exe'

Below is the extended usage to show file with desired extension: 
- test2.sh 

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1. #!/bin/sh  
2. EXT=$1  
3. ARRAY=($(ls -1 test/*.$EXT))  
4. echo "List file with extension($EXT):"  
5. for f in "${ARRAY[@]}"  
6. do  
7.     echo -e "\t$f"  
8. done  

Supplement 
* How do I assign ls to an array in Linux Bash? 
* nixCraft - Bash Iterate Array Examples