how to cat a text file and save it as a variable

mrobertson · 07-01-2005, 10:21 AM

Aluser,

take a look at the first post of this thread. If you ned more info let me know and Ill fill you in a little more

jlliagre · 07-01-2005, 10:22 AM

Quote:

Do you think this is the best way to go for what I am trying to do?

No if I stick to you first posting, where you specified twice you needed to save the file content in a variable ...

Yes, if you don't care about saving intermediate values somewhere ...

mrobertson · 07-01-2005, 10:25 AM

If I end up needing to save the contents in a variable....what would be the best way to do it?

jlliagre · 07-01-2005, 10:33 AM

Assuming you need to run the script for an arbitrarily length period of time, an array is probably a bad idea, it would be wiser to save the file content to the file system.

e.g.:

Code:

while true
do
  a="$(<filename)"
  echo "$a" | tee /somedirectory/filename.$(date +"%Y-%m-%d@%T")
  sleep 1
done

aluser · 07-01-2005, 10:41 AM

Quote:

Originally posted by mrobertson
Aluser,

take a look at the first post of this thread. If you ned more info let me know and Ill fill you in a little more

your first post says you need to save the file contents to a variable but not why. So, I don't know if you need to save it or not, and thus I can't tell if the loop with cat and not saving the file to a variable is what you want.

Sooooo, what is your script actually supposed to accompish? and why not just run these code snippets to see if they do what you want?

mrobertson · 07-01-2005, 10:53 AM

My script just needs to read a text file every second and print out whatever is in the file. I am debating as to whether I need to save the contents as a variable each time they are read or not. If you could give me an idea of how both would work....that is saving the contents as a variable and not saving as a variable...it would be greatly appreciated. Thanks for your time and help.

jlliagre · 07-01-2005, 11:00 AM

Quote:

My script just needs to read a text file every second and print out whatever is in the file.

This has been answered many times.

Quote:

I am debating as to whether I need to save the contents as a variable each time they are read or not.

That is your right.

Quote:

If you could give me an idea of how both would work....that is saving the contents as a variable and not saving as a variable...it would be greatly appreciated.

To save or not to save ... perhaps can you give us a clue of what you intend to do with the stored data ...

Quote:

Thanks for your time and help.

You're welcome !

aluser · 07-01-2005, 11:02 AM

a while back jllagre posted two equivalent snippets, one which saves to a variable and one which doesn't. The difference is that the save-to-variable one is slightly less efficient.

If you want to *do* something with that variable inside the loop, other than just echo it once which is effectively what cat does, then you should start with the snippet that saves to the variable.

If you only want to cat the file once every second, then by god just cat it once every secon

mrobertson · 07-01-2005, 12:40 PM

how do you get the code to execute?

I saved the code in a etc directory as sample. I did a cd etc.....then chmod 711 sample....then at the command line typed smaple and ./sample and it said no file exists. I did a ls in the etc directory and the file was there.. what could be wrong?

jonaskoelker · 07-01-2005, 01:24 PM

to OP: when *all* you want to do is cat a file every 2 secs, I'd recommend watch(1) (go play with it anyways--it's about just as cool as screen & wget

(okay, almost)). If it's part of something bigger, then a sleep-2-loop is probably better. You can also put the loop in the background:

Code:

while true; do
...
done &

Google for `advanced bash scripting guide'. I'd also like to suggest that you read "Smart Questions" (ESR)--especially the part about describing the goal and not just the step.

I understand that one of your goals is to learn, and that changes things a bit (from somewhat technical to somewhat... didactic/mental/psycological).

$ set CENTS="`seq 2 3 | head -n 1`"
$ whoami
jonas
$ exit

jlliagre · 07-01-2005, 02:01 PM

Quote:

I saved the code in a etc directory as sample.

Okay, but which code ? post it there just to be sure.

Quote:

I did a cd etc.....

Okay

Quote:

then chmod 711 sample....

Okay, well "chmod a+x sample" is clearer

Quote:

then at the command line typed smaple

Typo here ...

Quote:

and ./sample

Okay

Quote:

and it said no file exists.

What said that ?
Paste the full error message for us to understand what's going on !

Quote:

I did a ls in the etc directory and the file was there..

Okay

Quote:

what could be wrong?

Don't know, depend on the full error message and the script itself ...

mrobertson · 07-05-2005, 07:05 AM

Here is the code that I used:

Code:

#!/bin/sh

while sleep 1
do
  cat crap1
done

I was using telnet when trying to execute the code. The error message that I get is as follows:

-sh: ./sample: not found

It almost sounds like it may be from this line: #!/bin/sh

Let me know what you think?

keefaz · 07-05-2005, 07:09 AM

No as the error say : -sh: ./sample: not found
I think sh does not find sample script
You could try ls command to see if sample is here
before attempt to ./sample

bigearsbilly · 07-05-2005, 07:13 AM

even smarter?

Code:

tail -f filename

Quote:

SunOS 5.8 Last change: 18 Mar 1997 1

User Commands tail(1)

-f Follow. If the input-file is not a pipe, the program
will not terminate after the line of the input-file
has been copied, but will enter an endless loop,
wherein it sleeps for a second and then attempts to

read and copy further records from the input-file.
Thus it may be used to monitor the growth of a file
that is being written by some other process.

mrobertson · 07-05-2005, 07:16 AM

I did try that and the file was in the directory. Any other ideas?