bash 脚本 - 仅当不为空时才回显

Question

Is there an option or something I can use to encapsulate echo statements so that they don't print if the line is empty?

I was thinking something like:

myecho(str){
  if [[ -z str ]]; then
    echo str
  fi
}

but I couldn't find how to pass parameters.

Answer 1

Arguments to functions are passed like arguments to scripts. Starting at $1 until $n

myecho(){
    if [ -n "$1" ] ; then
        echo "$@"
    fi
}

myecho ""
myecho "foo"

Using -n in a test you can verify that a string is not empty. Learn more about functions in bash: http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-8.html

Answer 2

What about this?

[ -n "${STRING}" ] && echo ${STRING}

Or the complementer version:

[ -z "${STRING}" ] || echo ${STRING}

Or you can do some "echo magic":

echo -en "Some prependig text before the empty string: \""
echo -n "${STRING}"
echo -e "\" and some postfix text..."

Answer 3

function echo2() {
   if [ -n "$1" ]
   then
      echo "$1"
   fi
}

Answer 4

从man bash (Shell Parameter Expansion)，如果str不为空或未设置，则回显${str}\\n ：

echo -n ${str:+$str\n} # ${str+$str\n} also works

Answer 5

This should work:

echo. 

or

echo. SOMEVARIABLE_WHICH_WILL_NOT_OUTPUT_IF_EMPTY