if...else...statement

CyberIT · 09-24-2021, 05:58 PM

Im stuck on this if...else...statement.

Code:

usage ()
usage1 ()
usage2 ()

update ()
{
rm_hos1=$1
rm_info=$2
rec_type=$3

input ()
{
if [ rm_hos1=$1 ] && [ rm_info=$2 ]; then
  if [ $# -ne 2 ]; then
    usage
  fi

elif [ rm_hos1=$1 ] && [ rm_info=$2 ] && [ rec_type=$3 ]; then
  if [ $# -ne 3 ]; then
    usage2
  fi

elif [ rm_hos1=$1 ] && [ rec_type=$2 ]; then
  if [ $# -ne 2 ]; then
    usage1
  fi
fi
}

Code:

if [ "$rec_type" == "a" ]; then
  ...command
  ...command

elif [ "$rec_type" == "b" ]; then
  ...command
  ...command

else
  ...command
  ...command
fi
}

It fails on the bold if statement ... I dont know a way around.

First IF statement needs inputs 1 and 2.
Second IF statement needs inputs 1 and 2 and 3.
Third IF statement needs inputs 1 and 3 but not 2.

Please help. Thank you!

michaelk · 09-24-2021, 10:36 PM

Whitespace is important with if statements. Compare the second code block with yours and use shellcheck.net to check your syntax.

boughtonp · 09-25-2021, 07:01 AM

Michael is correct, and I'll note you can install shellcheck locally if you don't want to run it online, and there are even editor plugins available to make it even easier.

Also, simply saying "it fails" is useless - in future make sure to always give the actual error messages and/or describe in what way it is failing.

CyberIT · 09-25-2021, 08:24 AM

Quote:

Originally Posted by michaelk

Whitespace is important with if statements. Compare the second code block with yours and use shellcheck.net to check your syntax.

Thank you! I will do that and update...

CyberIT · 09-25-2021, 08:26 AM

Quote:

Originally Posted by boughtonp

Michael is correct, and I'll note you can install shellcheck locally if you don't want to run it online, and there are even editor plugins available to make it even easier.

Also, simply saying "it fails" is useless - in future make sure to always give the actual error messages and/or describe in what way it is failing.

Sorry about that... Here is what I get.

Code:

24-Sep-2021 15:34:52.469 dns_rdata_fromtext: buffer-0x7ff448cdce60:1: near 'b': bad dotted quad
invalid rdata format: bad dotted quad
syntax error

ondoho · 09-25-2021, 10:44 AM

Quote:

Originally Posted by CyberIT

Im stuck on this if...else...statement.

Code:

rm1=$1
rm2=$2
rec1=$3

input_validation ()
{
if [ rm1=$1 ] && [ rm2=$2 ]; then
  if [ $# -ne 2 ]; then
    usage
  fi

elif [ rm1=$1 ] && [ rm2=$2 ] && [ rec1=$3 ]; then
  if [ $# -ne 3 ]; then
    usage2
  fi

elif [ rm1=$1 ] && [ rec1=$2 ]; then
  if [ $# -ne 2 ]; then
    usage1
  fi
fi

Code:

if [ "$rec1" == "a" ]; then
  ...command
  ...command

elif [ "$rec1" == "b" ]; then
  ...command
  ...command

else
  ...command
  ...command
fi

It fails on the bold if statement ... I dont know a way around.

First IF statement needs inputs 1 and 2.
Second IF statement needs inputs 1 and 2 and 3.
Third IF statement needs inputs 1 and 3 but not 2.

Please help. Thank you!

Pretty much everything about the first code snippet is wrong.

Please tell us what you're trying to achieve, we might be able to assist.

CyberIT · 09-25-2021, 02:48 PM

Quote:

Originally Posted by ondoho

Pretty much everything about the first code snippet is wrong.

Please tell us what you're trying to achieve, we might be able to assist.

Why would my code in first block be wrong?

In the end, Im trying to achieve this...

by using these inputs

rm1=$1
rm2=$2
rec1=$3

First IF statement receives inputs 1 and 2. completes successfully

Second IF statement needs inputs 1 and 2 and 3. completes successfully

Third IF statement needs inputs 1 and 3 but not 2. completes successfully

CyberIT · 09-25-2021, 02:51 PM

not within this post but I had others suggest to use getopt and getopts commands.

CyberIT · 09-25-2021, 03:00 PM

Quote:

Originally Posted by michaelk

Whitespace is important with if statements. Compare the second code block with yours and use shellcheck.net to check your syntax.

Whitespace was pretty much the issue here. Comparing the two blocks of code, I ended up updating these lines

Code:

if [ rm_hos1 = $1 ] && [ rm_info = $2 ]; then

Code:

elif [ rm_hos1 = $1 ] && [ rm_info = $2 ] && [ rec_type = $3 ]; then

Code:

elif [ rm_hos1 = $1 ] && [ rec_type = $2 ]; then

I also added the following code under my inputs...

Code:

update ()
{
rm_hos1=$1
rm_info=$2
rec_type=$3

input ()
{
if [ "$rec_type" == "a" ]; then
  rm_info=$2
  rec_type=$3
else
  rec_type=$2
fi

I went off on a tangent of redoing my code due to a suggestion to use getopt and getopts commands. along with shift
That got a bit confusing to me so I decided to play around and see if some other IF statements would do it under the inputs section of my code.

I had it stuck in my head that I needed to "skip" input #2 which is what I wanted to do but went a different way of doing so.

astrogeek · 09-25-2021, 03:06 PM

Quote:

Originally Posted by CyberIT

not within this post but I had others suggest to use getopt and getopts commands.

Those are very good choices if you have more than a very few options to handle, want to offer option variants such as short and long versions or have options which require arguments.

getopts is a bash shell built-in and you can find detail in the bash man page.

getopt is a GNU utility (my personal favorite) which gives you support for long options, optional or required arguments, etc.

But to use either you will need to understand basic shell scripting which is not evident from the code fragments in your original post. As noted already, most of the code you posted is simply wrong and if some of the tests seem to be working then that is really just lucky, or perhaps unlucky coincidence.

The ABS might be a good place to begin learning bash shell scripting. Don't let the "Advanced" part scare you off, it is really a good guide. And I always suggest learning your way around the bash man page - it is long but that is because it is comprehensive, complete and well organized! Learn your way around it and it will become you best resource!

Before offering advice on how to fix your existing code it would be helpful to know what is in those positional arguments, $1, $2 and $3. Are they numbers, or strings of characters? Are they passed from the command line or is this inside a function or are they set earlier in the script? Are you testing the actual value or just testing whether they are set or not?

CyberIT · 09-25-2021, 03:46 PM

Quote:

Originally Posted by astrogeek

Those are very good choices if you have more than a very few options to handle, want to offer option variants such as short and long versions or have options which require arguments.

getopts is a bash shell built-in and you can find detail in the bash man page.

getopt is a GNU utility (my personal favorite) which gives you support for long options, optional or required arguments, etc.

But to use either you will need to understand basic shell scripting which is not evident from the code fragments in your original post. As noted already, most of the code you posted is simply wrong and if some of the tests seem to be working then that is really just lucky, or perhaps unlucky coincidence.

The ABS might be a good place to begin learning bash shell scripting. Don't let the "Advanced" part scare you off, it is really a good guide. And I always suggest learning your way around the bash man page - it is long but that is because it is comprehensive, complete and well organized! Learn your way around it and it will become you best resource!

Before offering advice on how to fix your existing code it would be helpful to know what is in those positional arguments, $1, $2 and $3. Are they numbers, or strings of characters? Are they passed from the command line or is this inside a function or are they set earlier in the script? Are you testing the actual value or just testing whether they are set or not?

what is in those positional arguments, $1, $2 and $3. Are they numbers, or strings of characters?
They could be numbers or characters

Are they passed from the command line or is this inside a function or are they set earlier in the script?
they are command-line when the script is ran on server manually
if the script is called by something else then there will be arguments being passed in for those inputs

Are you testing the actual value or just testing whether they are set or not?
$1 is a value that will not change after input
$2 is a value that could be updated after input
$3 is a value that will not change after input however the outcome, scenario depends on the input

michaelk · 09-25-2021, 03:53 PM

Quote:

what is in those positional arguments, $1, $2 and $3. Are they numbers, or strings of characters?
They could be numbers or characters

Yes...
https://tecadmin.net/tutorial/bash-s...and-arguments/