Questions[tail](ubuntu)

Why is there a difference between the meaning of NUM in head -c and tail -c?

I will clarify what I mean with the following commands:

$ echo "words" | tail -c +1
words
$ echo "words" | tail -c +2
ords
$ echo "words" | head -c -1
words$ echo "words" | head -c -2
word$

The first command does nothing.
The second command removes the first letter.
The third command removes the newline.
The last command removes the last 2 characters including the newline.

So why does head removes 2 bytes when using -c and tail only one. This looks like some real inconsistency or is there an underlying meaning?

I would like a tail -f type of behavior that reads the entire file and then continues to follow it as it's written to.

SOLUTION

Based on the answer I accepted, this works: tail -f -n +1 {filename}

Why it works: The -f option continues to "follow" the file and output new lines as they are written to the file. The -n +1 instructs tail to start reading the file from the first line. Using -n -10 would start with the last ten lines of the file.

tail -f will update the file once new data is inserted , but if the whole file is being rewritten it will give an error .

is there any other option to keep reloading the whole file ?

Thank you

Let's say we do:

tail -f  /var/log/apache2/error.log

Then we see what we want to see, and then, we want to quit, so that we can navigate to other directories and so on... So, the question is:

How can we quit tail ?

I've tried to type: 'q', and 'exit', and 'quit', and 'kill', no luck.

I have a web application that outputs to a number of log files with performance information. One log file outputs code execution times and another outputs SQL timings. I have no control over the logger or the code that produces the log files, but I want to output the logs in one place.

Currently I am doing something like this

tail -f sqlLogs.log | grep sql-time
tail -f perflogs.log | grep exec-time

This outputs something to the console every time an SQL is executed in the application. But I have to run the code in two separate SSH sessions. However, what I want to be able to tail both files, in the same SSH session. Is this possible?