Programming :: Storing Output Of "time" Command To A Variable
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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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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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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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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May 23, 2010
I want to use PROMPT_COMMAND variable to build a history of all the commands i execute. So Basically i want to append the last executed command to my own command log file. How can i find the last executed command ?
I want to add PROMPT_COMMAND="echo $last_executed_command >> my_command_log" But I am not sure how to find the last executed command
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Feb 11, 2011
I would like to put a variable in the $PS1 prompt that will change each time a command is run. I want the color of the $PS1 prompt to change each time a command is run.I know that I can do this:
Code:
PS1="h@w # "
## "#" is changes every time a command is run
[code]....
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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 $a
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Mar 26, 2011
For example, when using bash you can use
Code:
to execute the previous command or
Code:
!<number> to execute the Nth command(use history to see the list). Or you can use
Code:
cd !-2:1
to cd into the value in the first field that was executed 2 commands ago Anyhow, say I run a command and the output is a path. Any way to cd and then some variable where OUTPUT of the previous command was stored? A variable that always stores the OUTPUT of the last command.
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Jan 10, 2010
New to ubuntu and shell scripting in general... currently I stored some data into a text file. Right now, I would like to output the data from the text file and store it into a variable. Here's what I have so far:
READ_FILE=$(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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Apr 20, 2010
I was reading that if I want to do a one time scheduled command, I should use at, which I've never done, as opposed to cron, which i'm kinda familiar with. But what I want to do is reboot my server at 3am tomorrow and force it to check the file systems with a shutdown -rF. For this do I even need to use "at" or could I just say shutdown -rF 3:00.Will that also know that I mean 3am tomorrow and not say in 3 minutes from now or 3pm?
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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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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 $USER")
but the variable remains empty.
What is the correct code?
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Feb 27, 2011
logging in a server through putty in the same network when i executed last command its showing system ip logged in time and logged out time the output as followsthis is my system
oot pts1 xx.xx.xx day month date time in time out timeand similarly am geeting other than this likeroot :0day month date time still logged in this is from more than 3 days its logged in
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Nov 19, 2008
suppose i store the history number of a command say :
1004 cat file
Then now i want to run it like : !1004 but by using a variable.
command=1004
!$command
i am getting errors like :
command=1004command
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Jan 14, 2010
I want pass a variable at compile time.
for example in x.c
int global_var = POSITION;
How can I send this POSITION at compile time. ie like # make POSITION=10 Is it possible?
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Apr 14, 2011
i'm trying to execute a shell script, i'm trying to use the values in an array for use in a sed command:
sed -n '/Sales ID: ${array[$i]}/,/Totals:/p'
that command creates empty files. so my guess is that its not recognizing the array as an array but as text?
how would i be able to utilize the array in the command? i got it, didnt think that if i doubled up the single quotes that it would work, but this worked:
sed -n '/Sales ID: '${array[$i]'}/,/Totals:/p'
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May 3, 2011
Let's say I am pinging a host, and want to output to a file each reply and its timestamp of when this started.
I know that it can be done with a loop and a shell script. Something like this
DO
echo "$(date)" >> results.txt ###includes the time and outputs results to txt###
ping -c 4 HOST >> results.txt ###a total of 4 pings at a rate of 1 per second###
REPEAT UNTIL USER PRESSES CTRL-C
Now, my first issue is that I need to be able to see results real-time as well.
Is there a way one can print to BOTH a screen and output? If one uses the ">>" command, it is essentially sending everything to the file. Running another ping command in parallel is not an option.
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Oct 20, 2010
I am using gtk to program GUI. How can I show the output of shell command into a textbox, ex ps -efc command ?
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Jan 28, 2010
Code:
ls Again the command can be stored in a variable and then executed. Like
Code:
var=ls
&var
The above two codes are the same. The problem occurs when we try to pipeline it. Consider the following problem:
Code:
ls | grep *
works fine...but when we try to store it in a variable and run the command there is an error.
Code:
var="ls|grep *"
$var
how to store this kind of commands in a variable?
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Apr 23, 2010
i am trying to print the time in ms using the gettimeofday function, but on execution the shell gives: Segmentation fault (core dumped) error and leaves the program.. here is the code:
struct timeval time1,time2;
double time_used1;
//get time1
gettimeofday(&time1, NULL);
[code]....
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Aug 7, 2010
I want to display 4 options using the case command and refresh the screen when options 1 and 2 are chosen (no changes to the options and you get asked again to chose option), but give a message for option 3 and exit on option 4. I set this up with the script below, but choosing option 1 works and choosing option 2 exits the script.
Code:
#!/bin/bash
#testing options
Option="0"
[code]....
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Dec 23, 2010
I have the following code :
Code:
E_BADARGS=65
if [ $# -ne 2 ] ; then
[code]...
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Mar 1, 2011
I am having all sorts of trouble trying to assign a variable within an awk script with the system command. I know there is a lot of ways around this problem, but for efficiency reasons, I would like to, within my awk script, do something like
system(x=3)
or
system(x=NR)
and, latter on the shell script which calls the awk script, use the variable $x. But nothing is passed to x. I have already tried things like
command = "x=3"
system(command)
and also used a pipeline within the system to pipe it to /bin/sh In fact tried a lot of stuff like that, using $(( )) etc etc etc I can create directories e write to files (yes, i could write to a file and read from there, but I dont think it is efficient, plus I am puzzled).
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May 4, 2010
I'm trying to create a program that would locate the oldest file of a certain type on a server. Here's the commands:
OLDEST_PATH=`find -L / -depth -maxdepth 6 -mindepth 6 -type d | sort -f | head -1`
OLDEST_FILE=`find -L $OLDEST_PATH | grep .mp3 | sort -f | head -1`
ls -al $OLDEST_FILE
I'm writing this all in expect but I'm having problems. The main problem I have is whenever I try to run the first command, I can't seem to isolate the result of the OLDEST_PATH so that the 2nd command will work. There always seems to be a newline in the variable and the result is only "find -L" command running and it bypasses the variable. If I can just figure out how to get the 1st and 2nd command to work, then I can figure out the 3rd. Here's some code:
Code:
send "find -L / -depth -maxdepth 6 -mindepth 6 -type d | sort -f | head -1
"
sleep 20
expect -re "(.*)
[Code]....
I know there is a better way to write this. I've tried multiple ways and this just happens to be the last way I've tried it. If you try running this, you'll notice that there is still carriage returns after the result of OLDEST_PATH and it prevents the 2nd "find" command from working properly.
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Jan 28, 2010
Was trying to write a shell script that has if conditional statements to decide different arguments for a command.Basically:
Code:
if [ "$1" = 1 ]
then
[code]...
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Jun 15, 2010
I have the following TCL code:
if{ [catch {sqlite3 db /path/to/db/file} result] } {
puts stderr $result
} else {
do something
}
What I want is to use a variable for the file name/path. When I put in a variable instead of the absolute path, I get an error: "missing close-brace: possible unbalanced brace in comment while executing"
This is weird because when I run the code with the fully qualified pathname, it works fine. I substitute out the pathname for a variable containing the pathname ($variable) and I get this error.
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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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Feb 12, 2011
I'm trying to execute the following command within a bash script:
Code:
tac /var/log/system.log | head -1
The script I wrote is:
[code]...
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Jun 13, 2010
The output of a command changed and I need to extract the data and print it out in a different fassion:
Code:
abcd1=aaaa xx
abcd 2 aaa xx bbb
abcd2=aaaa xy
ab 2 xx aaa bbb ccc xxx
should be transformed to:
[Code]...
Currently I used sed "search1|search2|search3" to get the lines that need to be transformed. But I also need to search for substrings in those lines and I need to print those substrings in a specific order together with other characters. How is this done with sed?
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