echo

echo is used to output whatever it is given into stdout. Often useful see the value of environment variables.

$ echo "Hello World!"
Hello World!
$ echo $USER
<your username>

Useful Options / Examples

echo -e [string...]

$ echo "Hello \tWorld\n"
Hello \tWorld\n 
$ echo -e "Hello \tWorld\n"
Hello   World 

$
Break it down
  • The -e flag will have echo evaluate the escaped characters inside the string. \n will be printed as a newline instead of as the literal characters.
  • This flag is also needed to use color in the output. Otherwise the values will be printed instead of interpreted.

echo [string...with color]

$ echo "\033[31mHello \033[36mWorld\033[m"  
\033[31mHello \033[36mWorld\033[m
$ echo -e "\033[31mHello \033[36mWorld\033[m"  
Hello World
$ echo "$(tput setaf 1)Hello $(tput setaf 4)World$(tput sgr0)"
Hello World
Break it down
  • There are two examples of adding color to echo output. The first requires the -e flag since it works with raw escape codes. Otherwise the values will be printed instead of interpreted. The second, using tput is considered to be better since it is more portable and much more readable. Note that it does not require the -e flag.
  • The final value resets the color, \033[m and $(tput sgr0), to the default so that the color does not run into your prompt.
  • tput setaf sets the foreground color, the text color. tput colors go from [1,7] by default but can be bumped up to [1,256]

echo -n [string...]

$ echo -n "Test "; echo "Should be on the same line"
Test Should be on the same line
Break it down
  • echo default prints a newline at the end of the input string.
  • The -n flag will have echo not print the new line character at the end.

echo $(expression)

$ echo $((1 + 1))
2
$ $((1 + 1))
-bash: 2: command not found
Break it down
  • echo can also be used to print the output of expressions that would not put their result into stdout.
  • This will keep bash from trying to interpret the output as command.
  • The idea behind this is very similar to the first example of printing out a environment variable
  • If you’re building a complicated bash command precede it with echo to make sure all the variables and expressions expand in the expected way.