reading the last line of a file

[Anon]

hi,
i am in a bit of a dilema. I have a file in the format :

field1:field2:1
field1:field2:2
field1:field2:3

what i want to do is this, i want to be able to read the last line (field1:field2:3) and then write a new line after it but by adding 1 to the last value:

so the file would have an extra entry at the bottom of the file:

field1:field2:1
field1:field2:2
field1:field2:3
field1:field2:4 // new line added

(you will notice that 1 has been added to 3 to get 4 on the next line)

Does anyone know how to do this?

I would appreciate any help!

Thanks,
Khilan

[Anon]

use the php function error_log() to append the line, but to get the last value, try using tail under unix.

[Anon]

Hello,

under Unix/Linux, I'd use a system call in a way like this:
"tail -n 1 filename"
Therefore see the syntax for the function "system()" in the PHP Documentation. The return-string I would grep, otionally typecast an increment, something like this:

$contents = explode (":" , $returnString);
intval($last_int) = $contents [2];
$last_int++;

And now you only have to concat your final line and append that to the original file. See the core file functions (fopen, fwrite etc.) for details.

Hope it works,

[Anon]

hey im still not sure of how to do this.. so your saying.. do something like this.. ??

$returnString = "system(tail -n 1 file.txt)";
$contents = explode (":" , $returnString);
intval($last_int) = $contents[2];
$last_int++;

$fd = fopen(file.txt,"w");
fputs($fd,implode(":",$returnString));

fclose($fd);

i can sense that some errors are present in there but not sure what, could you please help me out.

thanks alot!
khilan

[Anon]

Well,

I think you have to remove doublequotes around the system()-call. It have to look like this:

$returnString = system("tail -n 1 file.txt");

This function returns a string of the complete output of the last operation. That's why, we use the "-n 1" option to tail only the last ONE line of the given file.

Further I think the intval function should work better on a single line, or, for the first trial, better don't use it so far (of course you have to be sure that the last field of your file-row is really a number and it can be converted into integer!)

So, hope it works now, if not, I'll check it out and code that snippet for you and then I can give you (hopefully) a full functioned snippet .... :-)

greetigs from Germany,
Michael.

[Anon]

hey!!

ok , i am still having problems, this is what i currently have in my script (just to see if this thing works)...

<?php

$returnString = "system(tail -n 1 file.txt)";
$contents = explode (":" , $returnString);
$number = $contents[2];
$contents++;

$new_user = $number + 1;

$lineArr[]="test:test:".$new_user."\n";

$fd = fopen(file.txt,"w");
fputs($fd,implode(":",$lineArr));

fclose($fd);

echo "done";

?>

however, what happens is that it doesnt open the file.txt file, it creates a file called filetxt for some reason. And it creates the entry .. test:test:1 in it, but if i run the php file again, it doesnt do anything.

any ideas?

thanks,
khilan

[Anon]

Yes, I have an idea,

if you're writing file.txt it means:
concat "txt" and "file", because of the "." (point-operator).
Correct open syntax in your case is:

$fd = fopen("file.txt","a");

[Anon]

hey, okay i am getting a step further now. it is opening the right file but it only inserts :

test:test:1

despite there already being the following entries:

field:field1:500
field:field1:300

when i refresh the script it just adds test:test:1 again under the one it already added.
so the file looks like this:

field:field1:500
field:field1:300
test:test:1
test:test:1

any ideas? could u possibly have a look at the code i posted in the previous post because i think it has something to do with what i assigned to the $number variable.

thanks alot,
Khilan