input / output

• file I/O takes a form of stream of bytes
• anything on the system that produces or accepts data is treated like a file - e.g. disks, networks, terminals

standard I/O

• input stdin
  • input from keyboard
• output stdout
  • display on screen
• error stderr
  • display on screen

data filtering utilities

utility	function
cat	copy input to output
grep	search for strings in the input
sort	sort lines in the input
cut	extract columns in the input
sed	perform editing on the input
tr	translate char from the input to other char on the output
awk

I/O redirection

• > stdin redirection
• < stdout redirection

deploy@vmi2682430:~/test$ echo 'this is a test file # 1' > file1
deploy@vmi2682430:~/test$ cat file1
this is a test file # 1
deploy@vmi2682430:~/test$ cat < file1 > file2
deploy@vmi2682430:~/test$ cat file2
this is a test file # 1
deploy@vmi2682430:~/test$

pipelines

• initiate command1
• redirect command1 stdout to command2 stdin
• redirection command2 stdout to commandN stdin

pipeline

command1 | command2 | commandN