Compse commands with pipe
# List all folders and files in current dir
% ls -l
total 56
-rw-r--r-- 1 zwt staff 51 May 16 22:35 data.txt
-rwxr-xr-x 1 zwt staff 159 May 19 10:52 example.sh
-rw-r--r-- 1 zwt staff 123 May 16 22:25 example.txt
-rwxr-xr-x 1 zwt staff 251 May 19 11:00 example2.sh
-rw-r--r-- 1 zwt staff 38 May 21 21:31 hello.txt
-rwxr-xr-x 1 zwt staff 105 May 19 11:12 if.sh
-rwxr-xr-x 1 zwt staff 162 May 19 11:19 list_regular_files.sh
drwxr-xr-x 4 zwt staff 128 May 16 22:20 test_directory
-rwxr--r-- 1 zwt staff 0 May 19 10:35 testfile
# count how many folder and files in current dir
% ls -l | wc -l
10
% ls -l *.txt
-rw-r--r-- 1 zwt staff 51 May 16 22:35 data.txt
-rw-r--r-- 1 zwt staff 123 May 16 22:25 example.txt
-rw-r--r-- 1 zwt staff 38 May 21 21:31 hello.txt
# only count txt files
% ls -l *.txt | wc -l
3
