Ok, I'm going to try your examples. This is not trivial for a starter. I've just been reading but not practicing much, so this is not clear at first sight!
--- Post updated at 10:02 PM ---
I don't fully understand what you mean by:
and
.
I need to read about expansions!
Fortunately this stuff is pretty well documented. I'd start with Shell Expansions, it's probably best while reading this to have a shell handy and try out the different expansions/substitutions mentioned with something like the pparm script posted above. Ensure you understand why they shell works the way it does.
For example word splitting occurs before pathname expansion, so when a file containing white space is expanded it wont be split.
Parameter and variable expansion occurs before word splitting so variables with white spaces are split:
Code:
$ ls
jason_expand pparm 'test with space'
$ ./pparm test*
Param 1: test with space
$ VAR="test with space"
$ ./pparm $VAR
Param 1: test
Param 2: with
Param 3: space
$ VAR=test
$ ./pparm ${VAR}*
<work thru the manual and decide what will happen here before trying it>
Last edited by Chubler_XL; 09-26-2019 at 09:04 PM..
These 2 Users Gave Thanks to Chubler_XL For This Post:
Yes, I understand your suggestion but I would like to know what is wrong with the 'test' I'm using there! It's so simple that I can't understand why it's not working!
Edited;
In the meantime I did another test with my code. I used 'if...then...fi' and it works... :s
Yes, I understand your suggestion but I would like to know what is wrong with the 'test' I'm using there! It's so simple that I can't understand why it's not working!
&& and || control operators examine the exit status last command executed in the list.
If the last command has a zero exit status then a command following && will run:
if the exit status is non-zero then the command following || will run:
Code:
$ [ 1 -eq 0 ]
$ echo $?
1
$ [ 1 -eq 0 ] || echo no
no
This is fairly straight forward so far. However when you string 2 control operators together like this:
Code:
$ [ 1 -eq 0 ] || echo no && echo yes
The exist status of the test is non-zero so echo no is executed. Following this the exit status of echo no is examined and found to be zero so echo yes is then executed.
For this reason I avoid stringing && and || control operators together in a single command line.
I don't mind stringing multiple && control operators together, this has the effect of continuing executing of each command as long as it's predecessor succeeds:
Code:
command1 && command2 && command3 && command4
--- Post updated at 01:07 PM ---
As a side note I'd like to discuss the code presented by Stomp earlier:
This works as intended because the command in the middle will always succeed (return a zero exit status) so the end command is not executed.
However, I feel this is a small time bomb waiting for someone to come along later, and because it isn't directly obvious that the execution of the 3rd command is dependent on the exit status of the 2nd (not the original test as many could assume) they change the 2nd command.
Example:
Code:
$ [ 1 -eq 1 ] && grep NotFound /dev/null || echo no
no
The above grep is just an illustration, any other command that has the potential to return a non-zero value would break the original intent.
This User Gave Thanks to Chubler_XL For This Post:
Hi All,
I am new to shell scripting, Need your help in creating a shell script which converts any unix command output to JSON format output.
example:
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Filesystem size used avail capacity Mounted
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Hello guys,
I want to parse a JSON file in order to get the data in a table form.
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"loc": "51.57,-0.0333",
"org": "AS6871 British Telecommunications PLC",
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All,
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Hello,
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I need help in writing a BASH SCRIPT of ls command.
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f2.jpeg
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#
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I couldn't find an existing thread that addressed this question, so hopefully this isn't redundant with anything previously posted. Here goes:
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09-26-2019
