CODEWITHSUNDEEP
linuxbashshellechodash-shell
Lincoln
Lincoln

Reputation: 43

"echo" output different answer by sh and bash

I ran my script using three ways and the output was different, could you explain to me why it works like that? Thanks!! Here is my script

#!/bin/bash
#Program:
#     This program shows "Hello World!" in your screen.
echo -e "Hello World! \a\n" 
exit 0

And if i run it by bash and ./ like bash sh01.sh the output is

Hello World!

However, if i use sh like sh sh01.sh it would be like

-e Hello World!

And Here is some other information

  1. OS: Ubuntu 16.04.3
  2. type sh -> dash

Upvotes: 4

Views: 1772

Answers (1)

pynexj
pynexj

Reputation: 20688

echo is not very portable (even Bash's echo may behave differently on different OSes which may use different default options when compiling Bash). You can use printf. According to posix:

It is not possible to use echo portably across all POSIX systems unless both -n (as the first argument) and escape sequences are omitted. The printf utility can be used portably to emulate any of the traditional behaviors of the echo utility [...]

I have this _echo() in my bashrc:

#
# _echo [-n] args...
#
function _echo()
{
    local eol='\n'

    if [[ $1 == '-n' ]]; then
        eol=''
        shift
    fi
    if [[ $1 == '--' ]]; then
        shift
    fi

    printf "%s$eol" "$*"
}

Upvotes: 4

Related Questions