This is my first question on StackOverflow. I am pretty sure it would have been answered already (it is a pretty dumb question, I think, as I just started to learn Linux scripting), but I did'nt succeed to find an answer yet.
Sorry for that.
Here is my problem: I try to use in a shell a number given in a property file, I have an error because the number is not taken "as it is".
I have a prop.properties file :
sleepTimeBeforeLoop=10
and a test.sh shell :
#!/bin/sh
. prop.properties
echo "time="$sleepTimeBeforeLoop
sleep $sleepTimeBeforeLoop
When I launch test.sh I have the following Output:
time=10
sleep: invalid time interval `10\r'
Try `sleep --help' for more information.
What I understand is that my properties files was correctly sourced, but that the property was taken as a string, with some special character to indicate the end of the line, or whatever.
How can I do to take only the "10" value?
Thank you in advance for your answer.
This is line endings issue / make sure your script files are terminated by \n (the unix way)
eg. write it in UNIX text editor or use a windows one capable of saving in "unix style"
Related
I have to perform some necessary steps before installing my package, such as taking back up of previous datastore snapshot.
For that purpose I'm using a %pre script as follows.
%pre
#!/bin/sh
--------
--------
stamp=`date +%Y%m%d%H%M%S`
echo ${stamp}
-------------
-------------
The output is as follows: 20161103123325OURCE
It is printing some random characters along with date. "OURCE" is not present anywhere in my spec file.
The same script works perfectly as standalone. The platform is CentOS7.
rpmbuild knows a whole set of macros. Apparently a certain macro is defined as:
%S = %SOURCE
I didn't manage to find something that tells rpmbuild not to expand that macro; but there is a way in tricking him not to do so. I know this is a little workaround, but it's the best I could come up with:
stamp=$(date '+%Y%m%d%H%M%''S')
note that I replaced the backticks with the recommanded $() invocation
I just inserted two '' to split the string in two parts; this avoids macro replacement.
If you escape the percent '%' in your date command with a second percent symbol '%%' as described at the following link, that should correct the behavior you're seeing with expanding %S to "OURCE" as you're seeing in your output.
stamp=`date +%%Y%%m%%d%%H%%M%%S`
See section "Writing a Macro" here
http://rpm.org/user_doc/macros.html
When I write:
echo 2*3>5 is a valid inequality
In my bash terminal, a new file named 5 is created in my directory which contains:
2*3 is a valid inequality
I want to know what exactly is going on here and why am I getting this output?
I believe it's obvious that I'm new to Linux!
Thanks
In bash, redirections can occur anywhere in the line (but you shouldn't do it! --- see the bash-hackers tutorial). Bash takes the >5 as a redirection, creates output file 5, and then processes the rest of the arguments. Therefore, echo 2*3 is a valid inequality happens, which gives you the output you see in the output file 5.
What you probably want is
echo "2*3>5 is a valid inequality"
or
echo '2*3>5 is a valid inequality'
(with single-quotes), either of which will give you the message you specify as a printout on the command line. The difference is that, within "", variables (such as $foo) will be filled in, but not within ''.
Edit: The bash man page says that the
redirection operators may precede or appear anywhere within a simple command or may follow a command. Redirections are processed in the order they appear, from left to right.
bash does the output redirection first i.e. >5 is done first and a file named 5 is created (or truncated if it already exists). The resultant file descriptor remains open for the runtime of the echo command.
Then the remaining portion, 2*3 is a valid inequality, runs as the argument to echo and standard output is saved in the (already-open) file 5 eventually.
To get the whole string as the output, use single or double quotes:
echo '2*3>5 is a valid inequality'
This is an example of output redirection. You're instructing the echo statement to, instead of writing to standard out, write to a filename. That filename happens to be "5".
You can avoid that behavior by quoting:
echo "2*3>5 is a valid inequality"
Say for example a script begins like this
#!/bin/bash
#$ -S /bin/bash
#$ -l hostname=qn*
and then later down the page the actual script comes into play. My question is what does the "#$" symbol mean or do?
Are you by any means running on a batch cluster? Like Sun Grid Engine? There might be special meanings in scripts intended to run as a batch job.
https://www.wiki.ed.ac.uk/display/EaStCHEMresearchwik/How+to+write+a+SGE+job+submission+script
Update:
above link blocks when used from stackoverflow.com (works from google.com)
alternatives:
http://www.cbi.utsa.edu/sge_tutorial
http://web.njit.edu/all_topics/HPC/basement/sge/SGE.html
Lines beginning with # are comments. The first line may begin with #!, but it's still a comment to bash and is merely used to indicate the interpreter to use for the file. All other lines beginning with # are absolutely unimportant to bash, whether the next character is $ or anything else.
They seem to be parameters for the Oracle (ex-Sun) Grid Engine, look at this SO question or this one.
They are heavily using these kind of comments.
Those line are important for queue systems like sbatch.
Is is possible to have the history of a specific user in one more file other than the default file mentioned as HISTFILE?
I would like to have as backup file if main file was removed and let it be like a backup for that one.
Regards,
Sriharsha Kalluru.
You can create a hardlink to the file
cp --link --verbose /home/$USER/.bash_history /somewhere/else/users_history
When the original file in his home is removed the file is still there and preserves the content from being lost.
Many times I've found myself using Ctrl-R in Bash to get a old command four times the terminal width, just to find out that too many days have passed and it's no longer in the .bash_history file. Here are two lines that will keep track of every command line you type at the bash prompt and use no external processes at all, just plain bash.
My first approach to this problem was increasing the maximum number of lines in the history to a very large quantity. But no matter how large it was, there was always a moment when I needed a long command I typed many months ago and it had already left the history. The current solution came to my mind when I learned about the PROMPT_COMMAND variable, a command that bash executes before showing each prompt. Here are the two lines:
export HISTTIMEFORMAT="%s "
PROMPT_COMMAND="${PROMPT_COMMAND:+$PROMPT_COMMAND ; }"'echo $$ $USER \
"$(history 1)" >> ~/.bash_eternal_history'
One goal I set to myself was to achieve it without using any external process, so bash wouldn't have to fork a new process after every ENTER pressed at its prompt. The first line sets the format of history lines to include the date as a Unix timestamp, so you can now when you typed every command. The second line, which is the core of the solution, first ensures that, if a previous PROMPT_COMMAND was set, it gets executed before our stuff and then appends a line of the format:
PID USER INDEX TIMESTAMP COMMAND
to a file called .bash_eternal_history in the current user home.
Adding the username, which at first seemed unnecesary, became useful later to distiguish between "sudo -s" sessions and normal sessions which retain the same value for "~/", and so append lines to the same .bash_eternal_history file.
I hope some of you find these two lines as useful as I do. :-)
Would hard links solve your problem?
Also you can read the man page here.
i would write a cronjob that copies the original histfiel to a backuplocation every minute or so. the you don't have to worry about defining a second histfile.
otherwise you could write every command the user enters to a alternate file
for this approach take a look here:
bash, run some command before or after every command entered from console
I am trying to parse a giant log file using node.js, the file does not seem to get '\n' but when I do set list in vi it shows me '$" at the end of every line, does anyone know what that is. I means can I split a string on that.
I would recommend checking out your file via
cat -v -e
which will show you all unprintable characters and line endings.
It happens when you do set list, so you should read :h 'list' instead of asking this here. Everything what you need to know about this $ is stated in the help.
Second question (splitting string on end-of-line) is answered in :h getline(). I also doubt that file really does not have a NL so write here how did you came to conclusion «the file does not seem to get '\n'».