Why not just use nmap? It's the right tool for this sort of task.
Anyway, after having a quick look at your script, I came up with:
Logic: Try and change things around so you have multiple nc commands running at once (in the background). After all, the majority of the runtime for a task like this is spent wating for the reply packets.
Instead of date | awk '{print $2" "$3" "$4" "$6}', you can use date "+%d %b, %Y %T"
thank you for the suggestions. i'm curious as to if all that "while looping" that im doing makes sense? is this how a more advanced user like you would do it?
i will incorporate your suggestions, however, i'm interested in making the while loop look more elegant. can awk be used for this?
Hey, I'm writing this bash script that will test print me many copies of the same program but with different combos of 4 variables being between 1 and 100. Here's the code:
#! /bin/bash
x=0
for ((a=1; a < 101; a++))
do
for ((b=1; b < 101; b++))
do
for ((c=1; c < 101; c++))
do
for... (4 Replies)
Good morning - I have publication lists from 34 different faculty members. I need to end up with the numbers of publications in common across all 34 faculty.
I need to grep person1 (last name) in list2, person1 in list3, person1 in list 4, etc., then person2 in list3, person 2 in list4, etc.,... (2 Replies)
I have to to read files simultaneously in two nested loops,but am getting error can anyone do the needful.
useridFile=userIds.txt
fname=kiran.txt
exec<$useridFile
while read line
do
echo "User IDs are..$line"
USER_ID=$line
REMOTE_DIR_LOCATION="/home/test/$USER_ID"
SOURCE_DIR=$USER_ID... (1 Reply)
I need help getting over this bump on how nested for loops work in shell. Say i was comparing files in a directory in any other language my for loop would look like so
for(int i=0;to then end; i++)
for(int y = i+1; to the end; y++)
I can't seem to understand how i can translate that... (5 Replies)
You can use one while inside another?
I made the following script (without really knowing if I can use two while) to get 3 numbers different from each other at random:
num1=$(( $RANDOM % 10 ))
num2=$num1
while
do
num2=$(( $RANDOM % 10 ))
done
num3=$num1
while
do
while
do... (1 Reply)
Ok... am going slightly loopy trying to get this working (no pun intended)
What I need is to modify this code which takes a string input then echo's each character on a seperate line, to do the same thing but to put DIGIT: in front of numbers and LETTER: in front of letters.
I know a regular... (5 Replies)
KSH isn't my strong suit but it's what my company has to offer. I've got a script with two nested loops, a FOR and UNTIL, and that works fine. When I add a CASE into the mix I end up getting "Unexpected 'done' at line xx" errors. Any suggestions on this?
for divi in at ce ci cm co de di fl... (9 Replies)
Hi experts,
I just want to know if there is a better solution to my nested while read loops below:
while read line; do
while read line2; do
while read line3; do
echo "$line $line2 $line3"
done < file3.txt
done < file2.txt
done < file1.txt >... (4 Replies)
Greetings All,
The following script attempts to enumerate all users in all groups in the group file(GROUP) and echo the following information:
GROUP ---> USER
The script is as follows:
IFS=","
for GROUP in `ypcat -k group | cut -d" " -f1`
do
for USER in `ypcat -k group... (13 Replies)
It's been a while since I used csh formatting and I am having a little bit of trouble with a few things. Things seem so much easier to execute in Matlab, however I need to do this on the terminal because of the programs I am trying to interact with.
So here's what I want to do: I have a file... (0 Replies)
Discussion started by: katia
0 Replies
LEARN ABOUT PLAN9
flock
FLOCK(1) User Commands FLOCK(1)NAME
flock - manage locks from shell scripts
SYNOPSIS
flock [options] file|directory command [arguments]
flock [options] file|directory -c command
flock [options] number
DESCRIPTION
This utility manages flock(2) locks from within shell scripts or from the command line.
The first and second of the above forms wrap the lock around the execution of a command, in a manner similar to su(1) or newgrp(1). They
lock a specified file or directory, which is created (assuming appropriate permissions) if it does not already exist. By default, if the
lock cannot be immediately acquired, flock waits until the lock is available.
The third form uses an open file by its file descriptor number. See the examples below for how that can be used.
OPTIONS -c, --command command
Pass a single command, without arguments, to the shell with -c.
-E, --conflict-exit-code number
The exit code used when the -n option is in use, and the conflicting lock exists, or the -w option is in use, and the timeout is
reached. The default value is 1.
-F, --no-fork
Do not fork before executing command. Upon execution the flock process is replaced by command which continues to hold the lock.
This option is incompatible with --close as there would otherwise be nothing left to hold the lock.
-e, -x, --exclusive
Obtain an exclusive lock, sometimes called a write lock. This is the default.
-n, --nb, --nonblock
Fail rather than wait if the lock cannot be immediately acquired. See the -E option for the exit code used.
-o, --close
Close the file descriptor on which the lock is held before executing command. This is useful if command spawns a child process
which should not be holding the lock.
-s, --shared
Obtain a shared lock, sometimes called a read lock.
-u, --unlock
Drop a lock. This is usually not required, since a lock is automatically dropped when the file is closed. However, it may be
required in special cases, for example if the enclosed command group may have forked a background process which should not be hold-
ing the lock.
-w, --wait, --timeout seconds
Fail if the lock cannot be acquired within seconds. Decimal fractional values are allowed. See the -E option for the exit code
used. The zero number of seconds is interpreted as --nonblock.
--verbose
Report how long it took to acquire the lock, or why the lock could not be obtained.
-V, --version
Display version information and exit.
-h, --help
Display help text and exit.
EXAMPLES
shell1> flock /tmp -c cat
shell2> flock -w .007 /tmp -c echo; /bin/echo $?
Set exclusive lock to directory /tmp and the second command will fail.
shell1> flock -s /tmp -c cat
shell2> flock -s -w .007 /tmp -c echo; /bin/echo $?
Set shared lock to directory /tmp and the second command will not fail. Notice that attempting to get exclusive lock with second
command would fail.
shell> flock -x local-lock-file echo 'a b c'
Grab the exclusive lock "local-lock-file" before running echo with 'a b c'.
(
flock -n 9 || exit 1
# ... commands executed under lock ...
) 9>/var/lock/mylockfile
The form is convenient inside shell scripts. The mode used to open the file doesn't matter to flock; using > or >> allows the lock-
file to be created if it does not already exist, however, write permission is required. Using < requires that the file already
exists but only read permission is required.
[ "${FLOCKER}" != "$0" ] && exec env FLOCKER="$0" flock -en "$0" "$0" "$@" || :
This is useful boilerplate code for shell scripts. Put it at the top of the shell script you want to lock and it'll automatically
lock itself on the first run. If the env var $FLOCKER is not set to the shell script that is being run, then execute flock and grab
an exclusive non-blocking lock (using the script itself as the lock file) before re-execing itself with the right arguments. It
also sets the FLOCKER env var to the right value so it doesn't run again.
EXIT STATUS
The command uses sysexits.h return values for everything, except when using either of the options -n or -w which report a failure to
acquire the lock with a return value given by the -E option, or 1 by default.
When using the command variant, and executing the child worked, then the exit status is that of the child command.
AUTHOR
H. Peter Anvin <hpa@zytor.com>
COPYRIGHT
Copyright (C) 2003-2006 H. Peter Anvin.
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU-
LAR PURPOSE.
SEE ALSO flock(2)AVAILABILITY
The flock command is part of the util-linux package and is available from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils
/util-linux/>.
util-linux July 2014 FLOCK(1)