Programming :: Bash - Ps - Psgrep And Read /proc/$pid Make Script Exit
Mar 22, 2011
I have not been able to write bash to use a PID file to ensure no other instance of the same script is running! All three methods I can think of to see if the PID in the PID file is another instance of the script make the script exit with a return code of 1 but the same commands run at the command prompt work as expected.
The first attempt was:
Code:
The first attempted workaround was:
Code:
The second attempted workaround (with debug to make the following command prompt copy and paste meaningful) was:
Code:
Here's the command prompt session, testing with a stale PID file and then manually running the problem command and it behaving as expected:
Code:
This on Slackware64 13.1 which has bash 4.1.7.
In desperation I tried rebooting but the behaviour was the same.
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Dec 6, 2010
I have a requirement, to read the complete proc filesystem from the linux pc.. Does linux provide some functions to read the proc filesystem means the directories and files present in the filesystem.. in short I want to create a treeview of proc filesystem. and if a user selects the file in the proc.. I should show the contents in the respective file. So I want some library or functions to read the proc filesystem..
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Dec 8, 2010
I am trying to read the /proc/net/tcp6 file of a huge server (chat server) for monitoring the tcp6 connection states.
My server's tcp6 file has more than 26000 lines. For monitoring the server connections, my monitoring tool has to read the /proc/net/tcp6 file quickly in a regular interval (5 secs) and process. Presently it takes minimum 6-7 seconds for reading the whole file.
My tool can able to read the normal file (26,000 lines) less than 1 second, but it is not possible to read the same size of proc file.
I have 2 questions:
1) Why proc file takes more read time than normal file?
2) Is there any way to read the /proc/net/tcp6 file more quickly?
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Jul 22, 2010
is there a way to make the /proc filesystem writeable? With aufs or unionfs i can't join the /proc filesystem with a writable directory directly. But i think it should work by using one of this file systems.If i try to join two dirs write-proc and virtual-proc Code: mount -v -t aufs -o dirs=/tmp/write-proc/:/tmp/virtual-proc/ none /tmp/joined-proc/ and afterwards make a bind mount /proc to virtual-proc Code: mount --bind /proc /tmp/virtual-proc/ i can't see any change in /tmp/joined-proc.
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Jun 10, 2010
I am running a command pretty similar to the one below:
Code:
I need to capture the exit status of that part of the command.
What I am trying to do is set a variable that can be modified within my_job.sh, and used to exit.
However, no matter what I set "status" to in my_job.sh, it exits with "0".
What can I do differently?
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Mar 3, 2010
How exactly can I use the exit status of a command in an if statement ?
Something like this:
Code:
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Dec 26, 2010
I'm new to scripting and I have a trouble with if statement syntax. The code is: Code: #there is a diff command here, and it does what i want but#i wanna see 1 if the exit value of diff is 0, and otherwise i wanna see 0.#the problem is here: (syntax error near unexpected token "then")
if["$?"==0];
then
echo 1
[code].....
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Jul 1, 2010
Is there a way to count the number of errors- an exit variable $? from one function?
The output from the exit variable (either erroneous or correct (1) or (0)) is it possible to add the erroneous one ups?
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Jan 24, 2010
simple bash code:
Code:
#!/bin/bash
trap "echo 'you got me'" SIGINT SIGTERM # to trap ctrl+c
echo "Press ctrl+c during 5 sec loop"
for ((i=0;i<5;i++)); do
[Code]...
How come code behaves normally and stops when ctrl+c signal is caught and resumes, but after I use at least one timeout read in the code it looks like, if signal is caught again it doesn't pause the execution but skips the loop. If you remove -t (timeout) option from the read, both loops look the same!
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Feb 3, 2011
I am trying to get bash script using zentity to exit if the user presses the cancel or close buttons.The exit codes are working fine; they read 1 or 0 depending on the status but it always assumes 0. This is the portion of the script: PHP Code:
function settings(){
result=$(zenity --height=30 --width=300 --list --checklist --title='Selection'--column=Boxes --column=Selections --column="Options"
[code]...
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Apr 11, 2010
I noticed that if I have "exit" in a bash script file., e.g. script.sh,that when the word "exit" is reached, and the script file being executed is not in the PATH nvironment, i.e. ". script.sh", the whole konsole shell profile is exited! What gives here? Is there another command compatible to "exit" to prevent this, or will I just have the leave the "." part in the PATH enviroment, which is, to my understanding, is not recommended? I desire for a "goto" function in bash script files
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May 22, 2010
In linux, creating thread is same as process (clone()), except the virtual address space gets shared with the parent.If a running main process(thread) creates new thread, and if main thread exits, why should the new thread too exit? both are different entities, The same doesn't happen if the child thread exits, the parent thread would be alive.
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Jun 3, 2010
I have been looking for a script example of reading and writing to the parallel port's data, status, and control registers using bash. I see it done in pascal, tcl, etc. but nothing in bash.
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Sep 24, 2010
Code:
test=(1 2 3 4 5)
for car in ${test[@]}
do
echo "Element : $car"
[code]....
if variable $car equals 1, new element is added "6" to an array. But i don't know why when i am printing all elements of this array (echo "Element : $car") this element ("6") is not mentioned, but if i make a command which check an amount of contained elements by array it will be 6 elements.
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Aug 8, 2010
I have a script that reads part of a line, delimited between the first and second intended part by a colon. Then it "chops" the part after the colon, which are words offset by commas (counting them beforehand so as to catch every word in the string's second part), like this:
Code:
"COLORS.JPG:red,orange,yellow,green,"
(Returning)
red
[code]....
single script that parses/breaks both parts of a line like this "COLORS.JPG:red,orange,yellow,green;blue,indigo,violet," so that the two parts, separated into single words (or two and three words, sometimes with spaces) can be used as single-line annotations and written to JPEG files using Exiv2. So far, I haven't been able to come up with a script that does this without one part of the total string(usually that part after the colon) becoming the first word in the second array. In other words, I look for this:
KEYWORDS:
[ ]red
[ ]orange
[ ]yellow
[code]....
Or vice-versa (ie, the second array winds up as a single-line "member" of the first). I think it's because I'm using a single while read loop to read the text file in which the filenames and substrings happen to be. If there's some way of reading a file once and going back to the beginning to read it again in another while loop, I haven't found it.
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Mar 14, 2011
I am struggling with Bash scripting at the moment (I can't seem how anyone can write scripts with this language!!!) I have a need at home to have a cron job execute daily to lookup my downloads.txt file, read each url (per line) and download content from that url. Then that entry needs to be removed (well I keep all urls in memory and clear the file afterwards). If an error occurred during the download process, then the url is written to a downloads.err file. I got all the above working except for properly reading the url from the text file without including newline characters. I am using the following to read:
while read url; do
--Do whatever here--
done < downloads.txt
How can I get it not to let the url variable have newline characters?
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Mar 28, 2011
I have a script that will ask the operator to specify whether the script should fetch the bits via FTP or SCP:
Code:
# Specify transfer method
echo "[setup]: Please specify file transfer method [ftp] or [scp]:"
[code]....
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May 7, 2010
As I'm starting to learn bash scripting I'm trying to automatize some tasks I usually perform. I have a notification mail I need to send several times a day. It has this structure:
Quote:
Dear user,
blah blah blah blah
You need to contact the following people:
[code]...
To replace "user", I found this:
Code:
read -p "Please enter username: " username
echo "Dear $username,"
Which probe to be very useful with other simple notifications like this. But I don't know how to manage the email addresses as they are usually more than one and could vary from 1 to 10. They should appear one above the other. I found this: "Here is a little work around. The only thing the user needs to do is hit enter without anything else on a line and it will close out"
Code:
#!/usr/bin/ksh
word=a
until [[ $word = "" ]];do
[code]....
I tried to use it and modify for my needs but I failed, I don't realize yet how can I use it. If possible, I would like to use the until loop like the above example just for learning purposes but any other form will be accepted as well.
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Nov 24, 2010
First, I made a simply script which let me download a file from a filehosting site on my server, but I can only put one link there, so I need help how to put multiple links in.Here is my script:
Code:
#!/bin/bash
echo "Enter URL:"
[code]...
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Mar 5, 2010
I have a fallowing simple bash script:
Code:
#!/bin/bash
echo -n "Please insert your name: "
read NAME
[Code]....
It works fine, but is it possible to have default values using bash read(1b)? I mean if user is prompter for sex, he just pushes ENTER and by default 'm' is chosen. Or if user is prompted for hometown and he doesn't insert anything, but just pushes ENTER button, 'New-York' sis chosen by default Are such default values possible in bash?
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Feb 13, 2011
I would like to find something portable that work on all machines. I have hmtl2text installed, and perl and sh.
Anyone would know if someone already made such thing to read new through the console ?
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Mar 11, 2011
For example, I have a text file with data which lists numerical values from two separate individuals
Code:
Person A
100
200
300
400
500
600
700
800
900
1000
1100
1200
Person B
1200
1100
1000
900
800
700
600
500
400
300
200
100
How would I go about reading the values for each Person, then being able to perform mathematical equations for each Person (finding the sum for example)?
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Feb 27, 2011
At my wit's end I can't find anything that I understand well enough to use. This is for a Unix class, we are working with shell scripting. File1 has 5 in it and File2 has 100 in it.The teacher wants us to read the values then do the math. This is what I have so far:#!/bin/bashvar1='cat File1'var2='cat File2'var3=`echo "scale=4; $var1 / $var2" | bc`echo The final result is: $var3
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Mar 25, 2010
I want my bash file to read from "input.dat" the two values emin emax. My input file looks like that:
#cat input.dat
!Energies
emin 10.00 !minimum energy
emax 30.00 !maximum energy
Now this seems to be not so hard with the command awk
#!/bin/bash
awk '{FS=" "}/emin/{print $2}' input.dat
awk '{FS=" "}/emax/{print $2}' input.dat
[code]....
So far so good. Now, I want to define two variables (e.g. e1,e2) in the bash file, so that their values would correspond to 00.00 and 30.00, as read from the input file. This one I have not found yet, thus asking for your advice. At the end, writing echo $e1 $e2, I should get 10.00 30.00 This is even harder to me: I want to replace the values emin,emax in a new file "modify.dat" which looks like that:
...
c---- energy interval
emin = 1.00
emax = 2.00
...
with the values e1 and e2 I have in my bash file. In other words, I want to call "modify.dat", find these two lines and replace the numeric values with the e1 and e2. At the end, my file should be like:
...
c---- energy interval
emin = 10.00
emax = 30.00
...
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Jul 22, 2010
AKA "zipping on the fly .. the slow-as-molasses way." The list includes full pathnames to each file, and they're all in subfolders of the same parent folder (which, unfortunately, is not the root folder of the drive or system on which the files reside). A cleaned-up and radio-ready portion of the list looks like
Quote:
.../taiga/ahqr-va-choyvp/bv0884-073.jpg
.../taiga/ahqr-va-choyvp/bv2635-073.jpg
.../taiga/ahqr-va-choyvp/bv3067-175.jpg
[code]....
What I'd like to be able to do is zip all the files in the list into a single archive, to avoid the step of having to copy them to the same location (presumably another folder on the HD) and then zip that folder. I'm more inclined to make provisions about extracting to a single folder at some other time. Is this possible in BASH, or would I have to consider a faster, more robust scripting language such as python or perl?
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Sep 23, 2010
Here's a challenge I've been struggling for months with:
I have a bash script that reads URL addresses of our internal server and then executes some test commands on them. Something like this:
Code:
read -p "Enter URL: " url
sh execute-what-ever-to $url
After copy-pasting the URL the user taps the enter key and the script proceeds, but here comes the tricky part: I want this to work without the need to press the enter key after copy-pasting the URL.
"read -n" does not work in this case, as the URLs vary greatly in length. However, the URLs always end to the same string. They could be like "http://url1/END", "http://url2/END" and so on. So this ending string "END" could be theoretically used to recognize that the whole URL has been pasted.
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May 29, 2011
PI'm trying to write a script to list all open ports in the MINIUNPND chain in iptables and use the procotol, port and destination ip to open ports on another router using upnpc.Here is the output of iptables -L MINIUPNPD
Code:
>iptables -L MINIUPNPD
Chain MINIUPNPD (1 references)
target prot opt source destination
ACCEPT tcp -- anywhere 192.168.3.124 tcp dpt:19955
ACCEPT tcp -- anywhere 192.168.3.124 tcp dpt:20054
ACCEPT tcp -- anywhere 192.168.3.130 udp dpt:10654
ACCEPT tcp -- anywhere 192.168.3.121 tcp dpt:29955
code....
No matter what i do i cant seem to remove the first 4 characters from the MYPROT array to leave only the digits. Also i cant seem to read the array back???
I thought it would simply be a loop reading each line and passing the fields in variables, executing upnpc commands i need then moving to the next line of the file until it reached the EOF.
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Aug 29, 2010
Trying to create a small script that will read user's input, test if user entered some input and if not display some message or display a text using user's input.
The script is the following but i get an error saying "[: 6: =: argument expected"
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Apr 18, 2009
I have a program I am writing where I have a for loop and I want to make it substitute the variable twice like:
for ((i=0;i<5;i++)) do
echo $"$i"
done
[code]...
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Aug 10, 2010
I've been using Digikam and it's a huge blow to my system memory. Even after quitting I still feel my computer to be slightly slower. I tried running the commands from [URL] but I get this instead
bash: /proc/sys/vm/drop_caches: Permission denied
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