Re: OT: Script to add line to file if it doesn't exist

[Mart Frauenlob <mart.frauenlob@chello.at>]

On 08.04.2010 14:58, Ron Johnson wrote:
> On 2010-04-08 03:01, Mart Frauenlob wrote:
>> On 07.04.2010 23:12, Ron Johnson wrote:
>>> On 2010-04-07 15:45, Mart Frauenlob wrote:
>>>> On 07.04.2010 22:10, Kent West wrote:
>>
>> [...]
>>
>>>>> I want a script that will read the file and look for the name "fred",
>>>>> and if it's found, leave the file alone, but if it's not found, to add
>>>>> the name "fred" to the bottom of the file.
>>>>>
>>
>>>> #!/bin/sh
>>>> grep -w "fred" file || printf "%s\n" "fred" >>file
>>>>
>>> Mart's method is the shell way.  The 3GL Way is:
>>>
>>> grep -w "$NAME" "$FILE"
>>> TMP=$?
>>> if [ "$TMP" = "1" ];
>>> then
>>>     echo -e "$NAME\n" >> "$FILE"
>>> fi
>>>
>>>
>>
>> May I ask what the 3GL way is?
>> All that is 'shell' scripting, right?
>>
> 
> Shell operators like &&, ||, |, > *implicitly* do "if" comparisons, open
> files for read/write, etc.
> 
> By "the 3GL Way", I mean a more explicit enunciation of each step.
> 

personally I choose the shortest way to write things in almost all cases.

if I only execute one command on true/false conditions, I prefer:
command && react_true || react_false

if reaction consists of multiple commands, I prefer:
if command; then
	...
else
	...
fi

using a temporary variable (and an extra assignment step) is only
reasonable for me, if I need to remember that one exit status later on
for whatever reason.

tmp=0
command || tmp=1
some_commands
...
if [ $tmp -eq 1 ]; then
	...
else
	...
fi

But yeah, many ways are possible, achieving the same result...

Best regards

Mart