function is not called correctly in bash

Question

I have this bash code that checks if the OS is Linux or Mac, and I use the function isWhat to be invoked from other functions.

function isWhat 
{
  if [ `uname` == $1 ];
  then
    return 1
  else
    return 0  
  fi
}

function isLinux 
{
    return isWhat("Linux")
}

function isMac
{
    return isWhat("Darwin")
}

However, I got these errors:

/functions.sh: line 13: syntax error near unexpected token `('
/functions.sh: line 13: `    return isWhat("Linux")'
runme.sh: line 7: isMac: command not found

What might be wrong?

Also, don't use the function keyword at all; it makes your script incompatible with POSIX sh for no good reason. isWhat() { is enough to start a function, and using that form retains compatibility with pure POSIX shells. — Charles Duffy
– Charles Duffy, Commented Nov 4, 2015 at 22:14
You've got other bugs in here too, by the way -- you're missing quotes around expansions (that one's a "real" bug, even if your only target is bash), and == isn't guaranteed to work inside [ ] by the POSIX standard (the standardized string comparison operator is =, not ==). Try running through shellcheck.net for an automated check for the quoting errors. — Charles Duffy
– Charles Duffy, Commented Nov 4, 2015 at 22:18
...and as a matter of practice, if you're writing something to be sourced in as an include file and using bash-only syntax, name it .bash, not .sh. — Charles Duffy
– Charles Duffy, Commented Nov 4, 2015 at 22:24

FatalError · Accepted Answer · 2015-11-04 22:13:24Z

5

That's not how you call functions in bash. They work just like other shell commands, i.e.:

function isLinux 
{
    isWhat "Linux"
}

Also, the return is redundant the function will return the exit status of the last command run. If you wanted to be explicit, you'd write it like:

function isLinux 
{
    isWhat "Linux"
    return $?
}

answered Nov 4, 2015 at 22:13

FatalError

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2 Comments

Charles Duffy Over a year ago

If we're pointing folks towards best practices, I'd tend to suggest POSIX-compliant function call syntax as well (isLinux() { with no function).

FatalError Over a year ago

@CharlesDuffy: Good point. OP did say bash but since the point of this is to detect platform, making it more cross platform makes a lot of sense, so I'd tend to agree.

prosseek · Accepted Answer · 2015-11-04 22:48:15Z

0

This is the working code after fixing some bugs.

function isWhat 
{
  if [ "`uname`" = $1 ];
  then
    echo 1
  else
    echo 0  
  fi
}

function isLinux 
{
    isWhat "Linux"
}

function isMac
{
    isWhat "Darwin"
}

The usage is (assuming the previous functions are in abc.sh)

source abc.sh
echo $(isMac)
if [ $(isMac) == 1 ];
then
    echo "A"
fi

I'm not sure exactly why, but I had to add function to make the code work anyway, I use Mac OS X 10.11.1.

edited Nov 4, 2015 at 22:48

answered Nov 4, 2015 at 22:39

prosseek

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1 Comment

FatalError Over a year ago

fwiw, the way you had it before with returns, if you swapped the 0/1 you could simply use if isLinux; then ... fi.

hookenz · Accepted Answer · 2015-11-04 22:13:06Z

-1

You're calling the bash functions incorrectly.

e.g.

return isWhat("Linux")

Should be

return isWhat "Linux"

etc

answered Nov 4, 2015 at 22:13

hookenz

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2 Comments

Charles Duffy Over a year ago

...and there's no point to the return; just making it isWhat "Linux" will pass the return value from the isWhat function through to the caller.

Charles Duffy Over a year ago

moreover, the documentation for return defines it to take an integer, not a command to call at all.

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