Programming :: Piping Cat Output To Variable?
Jan 10, 2010
New to ubuntu and shell scripting in general... currently I stored some data into a text file. Right now, I would like to output the data from the text file and store it into a variable. Here's what I have so far:
READ_FILE=$(cat $FILE_NAME)
This definitely works and READ_FILE has the necessary data. However, this command will trigger an output to std output and I will see data on the screen, which is not what I want. I tried:
cat $FILE_NAME | $READ_FILE
and various other variants of this. It does not output to std output but neither does anything gets stored into $READ_FILE. I tried:
cat $FILE_NAME >> $READ_FILE
and it arrived at an error of "ambiguous redirect".
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Jan 17, 2011
I have to save the result of ssh/grep into a file to keep the eol ("/n"):
ssh $SSH_OPTIONS $USER@$NODE "cd $LOG_DIR; grep -h '$pattern' log.*" > $file
So that when I grep on the local file again later, it can be printed out with original log lines. Otherwise, the log lines will be dropped and lines becomes concatenated into a single line, e.g., if I rewrite the script in this way, echoing the $result is not a good idea..
result=`ssh $SSH_OPTIONS $USER@$NODES "cd $LOG_DIR; grep -h '$pattern' log.*"`
is there some workaround that I can save it to a variable rather than file but still keep the eol? That will simplify my script and don't need to do all those I/Os!
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Feb 20, 2011
I have a bash script that calls a java class method. The method returns a string to the linux console when run independently. how can I assign the value from the java method to a variable in a bash script?running the script: java -cp /opt/my_dir/class.method [parameter]
output: my_string if added in a bash script:
read parameter
java -cp /opt/my_dir/class.method [parameter] | read the_output
echo $the_output
the above doesnt work, I also tried unsuccessfully:
the_output=java -cp /opt/my_dir/class.method [parameter]
the_output=`java -cp /opt/my_dir/class.method [parameter]`
java -cp /opt/my_dir/class.method [parameter] 2>&1
How can i get the output stored into the_output variable?
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May 16, 2011
I have the following code
Code:
ls ~/ | grep ^[[:lower:]]
and would like to take the result of this output and use this as the basis for a cp command to move these files to another folder.
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Apr 3, 2010
Suppose I want to account number of files beginning with abc , I can use "ls 'abc* | grep abc | wc -l", this will return me a number.
I want to store this number in a variable, say var1, so I tried
1. "ls 'abc* | grep abc | wc -l |read var1", but this didn't work as var1 has no value somehow.
2. var1='ls 'abc* | grep abc | wc -l', this just assign the entire string "ls 'abc* | grep abc | wc -l" to var1, which is not I wanted.
I don't want to store the value to a temporary file and then read the value from that file. I think there should be a direct way to get the value, but don't know how. I know in tcsh, one can just use set var1='ls 'abc* | grep abc | wc -l', but it also doesn't work in bash. Can anyone give any clue about this?
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Apr 30, 2010
how would you go about piping the output of the shell to notify-osd?
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May 12, 2010
I am looking for an alternative to cat for streaming the output (ATSC) of a dvb card to a file. cat works fine for a bit but there is some internal variable that reaches a size limit and stops it. As evident by the c error "variable has reached size limit" (sorry for the paraphrase I do not have the error in front of me.) That is ok, a co worker who knows c told me the best thing to do is to find some other utility to do this. cat /dev/dvb/adapter0 > test.mpg is what I am looking to replace. how to pipe this into some sort of compression utility.
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Jan 25, 2011
I'm trying to write a python script that will use the current user's name when interacting. Ex: when started, it should say "hello daweefolk" when I am logged in.
I've tried
Code:
username=os.system("echo $USER")
but the variable remains empty.
What is the correct code?
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Nov 11, 2010
I want to pipe the output of a command into grep as the search TERM, rather than the text to be searched, like this for example
Code:
cat /var/log/auth.log | grep date "&b &d"
so that I only see the lines in auth.log for the current day...but obviously that line doesn't work.... is there a way to do this with grep, or even another command?
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Sep 5, 2010
i'm building a dictionary with a bash script. it works perfect except i'd prefer something faster. btw i'm just piping the output to a file.
[Code]...
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Jul 28, 2010
I have two files :
FileA
prot1
prot5
prot9
prot15
[Code]....
What I need to do is to extract from fileB the fields containing only the strings in fileA.
I thought awk could do the job easily with :
Code:
awk 'BEGIN { RS = "###" } /'$variable'/' fileB > output
where variable would maybe be the output of grep from fileA. So can I store the output of grep in a variable to use it afterwards with awk ?
something like that:
Code:
result=`grep prot. fileA` ; awk 'BEGIN { RS = "###" } /'$result'/' fileB > output
but that doesn't work. I'm always getting the entire fileB.
The output of grep get stored in the variable, I verified that with echo. So there is something that I just don't get... It seems to me that the above line should work.
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Jan 21, 2011
In my script, I need to get execution time of a command (say 'ls') in mili seconds level. For this i tried using "time" command to retrieve the total execution time in milli seconds. But, the problem is that, how to save the output of time command in a variable. The format of the command is like "time ls -R /opt" Going further, the o/p of 'time' command is:
real 0m0.003s
user 0m0.004s
sys 0m0.000s
Here, in my script, I would like to use only middle line "user 0m0.004s" saved to the variable but unable to find out the way.
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May 1, 2011
My script.
This is may script:
Code:
Problem: Output file doest not exclude the values in grep -av
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Aug 6, 2010
I have my .procmailrc file set up to pipe mail to a simple php script I've written. The only thing the script does at this point is echo back a "hello" message. However, procmail does not execute the script properly.
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Dec 16, 2010
I have a bash script that I want to import in to Python, mainly just to see if I can or not. However in the script I do use some piping of commands into sed to trim it down to what I need. When I tried doing it with the os.system() call, it didn't work. The exact error is
sed: -e expression #1, char 16: unterminated `s' command
However the command that was run can be run in bash without an error. Is there a better/another way to do this? For reference the command is:
Code:
locate -n 1 wp-config.php | sed 's/wp-config.php/
/g' | sed '/wp-config.php/ d' | sed '/^$/ d'
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Aug 21, 2009
I'm trying to read content of file to variable and use this variable in for loop. The problem is, when I have c++ comment style in file - /*. Spaces in line are also interpreted as separated lines.
For example:
Code:
Changing $files to "$files" eliminate these problems but causes that whole content of variable is treated as one string (one execution of loop).
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Apr 7, 2010
my script has a variable which comes in the form +00.00 +0.00 -00.00 or -0.00 (the numbers can be any in that form) for any that have a + symbol I need to remove the +, but if it has a - symbol it needs to stay.
i need to make a new variable with the string from the old variable btut without any plus sign. I have tried a lot of different ways with no success, each thing I tried either left the + or removed the entire string. I think this should work but doesn't
foo=+12.40
bar=${foo#+}
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Apr 25, 2011
how I can search within a variable and assign the results to a new variable. I'll use the following as an example -
cars="Audi BMW Cadillac Chevy Dodge Ferrari Ford Mercedes"
list=`echo ${cars} | egrep -o '<A?+|<C+'`
with the echo command I get the following output assigned to list -
A
C
C
What I'd like to get for output is -
Audi
Cadillac
Chevy
how I could do this regardless of upper/lower case letters?
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Apr 28, 2010
included shell script inside c program, and i wanted to assign the value of c variable to shell variable..Can any one please suggest me how to do it?
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Feb 3, 2011
Kernel 2.6.21.5, GNU/Linux (Slackware 12.0).In this script,
Code:
semoi@darkstar:~$ cat rename4.sh
#!/bin/bash
INPUT="k3b_audio_0_04"
[code]...
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Mar 17, 2011
This loop is part of a bash script which takes multiple arguments.
Code:
for ((i=1;i<=$number;++i)) ; do
offset=$(($i+5))
[code]...
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Sep 8, 2010
I have a line that looks something like this:
Code:
How do i put its output in a variable?
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Mar 3, 2010
I tried using the tail command in my shell script and storing that value in a variable a but an error keeps coming. Is there any other way to store the output of a command into a variable. Cannot Read text from text file and store it in a variable using shell script. The thing is I need a number from the file new.txt and use that number in my script
#!/bin/bash
a = `tail -1 new.txt|head -n 1`
echo $a
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Feb 6, 2011
so i wrote myself a very simple hellworld program in c++
...the usual stuff
int main()
{
[code]...
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Mar 5, 2010
I need to store the output of bitset() in a variable ... is it possible in c++?
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Jun 8, 2010
how to set the subject of this up.. but here is what I am trying to accomplish (please keep in mine, this is only my first month playing with ANY Linux programming): My shared web host limits running 2 CRONS or 2 SSH sessions at one time. I need to run more than that.. So, my solution is to run what I need on my home computer, and then push all the results via SSH to my web server.
To keep things timed, I am trying to call 4 bash scripts from inside of 1 bash script... Each bash script has variables I need to export out to the remote (web) server. Being that I can only run 2 SSH or 2 CRON sessions on the remote, it wouldn't do me any good to open up CRON or SSH remotely or locally - either way I'm maxing out. That is why I would like to call 1 final script that takes the output of the 4 bash scripts and does the job.
Main bash calls via CRON every 30 minutes:
Code: ./script_1 &
./script_2 &
./script_3 &
./script_4 &
[code]....
I need to scp the file saved by wget to the remote server. I also need to pass the SQL statement generated in each script as a command in SSH. I'm lost how to get the info from "script_x" into a string that can be used to SSH - and doing this all inside of ONE SSH command. Would I store the SQL strings in a file and call that in the SSH command line?
If so, what is the command to make sure the variable output in the "script_#" file is sent to a file? Can I call the variable from the main Bash Script? Now - the good news is, I can SSH from my local machine to the remote one.That is about as far as I got.Again - I am so new to this that my ears are still wet. This has been something I have been working on for a while, and I'm just lost at this point.
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Mar 20, 2010
I'm trying to use the output from gdialog's input box in another command with no success. code...
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Feb 3, 2010
I would like to grep two numbers out of a text file, and divide them.
Here is the script code...
It feels like grep saves a new line too? or what is happening? i simply can't divide them, as it handles the variables as they are empty (and prints the two numbers although they were not printed
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Mar 26, 2011
For example, when using bash you can use
Code:
to execute the previous command or
Code:
!<number> to execute the Nth command(use history to see the list). Or you can use
Code:
cd !-2:1
to cd into the value in the first field that was executed 2 commands ago Anyhow, say I run a command and the output is a path. Any way to cd and then some variable where OUTPUT of the previous command was stored? A variable that always stores the OUTPUT of the last command.
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Feb 8, 2010
On command line I have no problem storing a variable e.g
Code:
:~/bin$ process=`ps -ef | awk ' $8 == "idesk" { print $2 }'`
:~/bin$ echo $process
26736
:~/bin$
When I try to incorporate this into a shell script I get a blank.
Code:
:~/bin$ cat process_idesk
#!/bin/bash
process=`ps -ef | awk ' $8 == "idesk" { print $2 }'`
[code]....
The process_idesk script has been chmoded to be executable by the user. I'm sure there must be a silly omission on my behalf.
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