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So I have a shell script math.sh which takes a number as an argument and echos one added to it and one subtracted from it:

#!/bin/bash

echo "Add: "$(($1 + 1))
echo "Subtract : "$(($1 - 1))

and my other shell script execute.sh is basically taking math.sh and a textfile as an argument and writing the output of math.sh to the text file.

#! /bin/sh
echo $1 > $2

However, the two echos are outputting to the text file on the same line as: Add: $(($1 ++)) Subtract : $(($1 --)) when I need it on separate lines like:

Add:$(($1 ++))

Subtract:$(($1 --))

How would I do this without editing math.sh? Because my execute.sh needs to be able to output any shell script to the text file, not just math.sh, on separate lines.

no_bashell
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  • Please add the code of the other shell script that is doing the printing, that's what is probably causing the bug (e.g. you could be echoing an unquoted variable). – user000001 Apr 20 '21 at 07:41
  • @user000001 hi, I've added the code now – no_bashell Apr 20 '21 at 07:45
  • Your `math.sh` script has errors in it (you can't change `$1` with `++` and `--`). Do you want your other script to take `math.sh` as its first argument, run it, and write the result to the second argument? If so, what about the argument that `math.sh` takes? – Kusalananda Apr 20 '21 at 07:51
  • @Kusalananda sorry, it was actually +1 and -1, theres multiple argument files Im trying to use execute.sh to run and didn't look at math.sh when writing my question, I just wrote it on the spot thinking I remembered its contents. – no_bashell Apr 20 '21 at 07:55
  • and also http://mywiki.wooledge.org/WordSplitting. `echo $foo` in effect changes all runs of whitespace in `$foo` to single spaces. Plus expands globs. – ilkkachu Apr 20 '21 at 09:00

1 Answers1

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The problem is the missing quotes, it should be:

#!/bin/sh
echo "$1" > "$2"

This is needed because otherwise bash will process any special characters inside the variable, such as spaces, newlines, asterisks (*), etc.

In this case the newlines were braking the argument into multiple arguments, causing echo to join them with a space.

Note that this is printing the first argument itself to the file.

To print the contents of $1 you would do:

#!/bin/sh
cat "$1" > "$2"

to print the output of $1 you would do:

#!/bin/sh
./math.sh "$1" > "$2"

If you also want the changes of the variables to be reflect in the current script, you can source it:

#!/bin/sh
. "$1" > "$2"
user000001
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  • Thank you so much!! I have been going crazy over this, I appreciate the help:) – no_bashell Apr 20 '21 at 07:48
  • This does not write the output of `math.sh` (if given as first argument) to anywhere. It may write the string `math.sh` to a file, but it would have done without the quoting fix as well. – Kusalananda Apr 20 '21 at 07:49
  • @Kusalananda: I was going by OP's source code, and sample output (for previous revision). I added a couple of more examples, not sure what OP is really after. – user000001 Apr 20 '21 at 07:53
  • Note for your last script: The `math.sh` script takes an argument. – Kusalananda Apr 20 '21 at 07:54
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    Sorry for the confusion, yes `execute.sh` takes another argument which it passes to `math.sh`. `math.sh` is just one of multiple files i need to pass to `execute.sh` so I didn't carefully look at math.sh's code, I just knew my consistent recurring problem was the lines kept outputting to the text file on the same line for math.sh and every other .sh file I was passing to `execute.sh` so @user000001 did fix that problem – no_bashell Apr 20 '21 at 08:01