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Shell script worked correctly until I added variable :(

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Top Forums Shell Programming and Scripting Shell script worked correctly until I added variable :(
# 15  
Old 01-22-2015
Are #! the first two characters of the file? No space before it or a line before it? What does ls -l /bin/*sh give ?
What happens when you call it like sudo /bin/bash ./ip full
# 16  
Old 01-22-2015
Quote:
Originally Posted by Scrutinizer
Are #! the first two characters of the file? No space before it or a line before it?
Hmmmmm, there is a space before the #!

Quote:
Originally Posted by Scrutinizer
Are #!What does ls -l /bin/*sh give ?
-rwxr-xr-x 1 root root 813992 Sep 26 06:55 /bin/bash
-rwxr-xr-x 1 root root 88340 Mar 30 2012 /bin/dash
lrwxrwxrwx 1 root root 4 Sep 26 06:55 /bin/rbash -> bash
lrwxrwxrwx 1 root root 4 Mar 30 2012 /bin/sh -> dash

Quote:
Originally Posted by Scrutinizer
What happens when you call it like sudo /bin/bash ./ip full
./ip: line 7: [: =: unary operator expected
./ip: line 17: [: =: unary operator expected

Different error. Is that space before the #! an issue? I love learning new stuff!
# 17  
Old 01-22-2015
Quote:
Originally Posted by gjws
Hmmmmm, there is a space before the #!



-rwxr-xr-x 1 root root 813992 Sep 26 06:55 /bin/bash
-rwxr-xr-x 1 root root 88340 Mar 30 2012 /bin/dash
lrwxrwxrwx 1 root root 4 Sep 26 06:55 /bin/rbash -> bash
lrwxrwxrwx 1 root root 4 Mar 30 2012 /bin/sh -> dash



./ip: line 7: [: =: unary operator expected
./ip: line 17: [: =: unary operator expected

Different error. Is that space before the #! an issue? I love learning new stuff!
That is the exact problem! The #! needs to be the exact first two characters. Otherwise it is a comment and it gets ignored...
So therefore the default shell got called instead which is /bin/sh which points to dash.
This User Gave Thanks to Scrutinizer For This Post:
gjws
# 18  
Old 01-22-2015
Quote:
Originally Posted by Scrutinizer
That is the exact problem! The #! needs to be the exact first two characters. Otherwise it is a comment and it gets ignored...
As I said, it's great to learn new things Smilie

Thank you, the script now runs without errors, and even better, I understand why!
This User Gave Thanks to gjws For This Post:
vgersh99
# 19  
Old 01-24-2015
If using = operator in test command, then you need value before it and after it.
If $1 is empty then you have nothing. => test cmd syntax error.
But "$1" is always something, sometimes string which length is 0.

Code:
# ex. make next change and no problem in syntax
#  if [[ $1 = "full" ]]
# =>
if [ "$1" = "full" ]

# 20  
Old 01-24-2015
Quote:
Originally Posted by kshji
If using = operator in test command, then you need value before it and after it.
If $1 is empty then you have nothing. => test cmd syntax error.
But "$1" is always something, sometimes string which length is 0.

Code:
# ex. make next change and no problem in syntax
#  if [[ $1 = "full" ]]
# =>
if [ "$1" = "full" ]

Not only that, but if $1 is left unquoted in the test command [ ... ], it will be subjected to field splitting and pathname expansion by the shell.
When using the double bracket bash/ksh/zsh shell grammar [[ ... ]], this will not be done...
# 21  
Old 01-24-2015
Quote:
Originally Posted by kshji
If using = operator in test command, then you need value before it and after it.
If $1 is empty then you have nothing. => test cmd syntax error.
But "$1" is always something, sometimes string which length is 0.

Code:
# ex. make next change and no problem in syntax
#  if [[ $1 = "full" ]]
# =>
if [ "$1" = "full" ]

Thank you, it's good to know the best practice. It's interesting that there is an error when using DASH, but no error when using BASH.

I wonder why systems don't link /bin/sh to BASH rather than DASH by default if BASH is a better shell?
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