I just wrote a ping sweep script in Bash this morning, and guess what: it's not working. Can you please check what it is that I'm missing.
Here's the script:
for i in `seq 1 255`
do
if ["$(ping -c1 -W1 -n 192.168.1.$i | grep '%' | cut -d',' -f3 | cut -d' ' -f2)" -eq "0%"]
then echo "Host live"
else echo "Host down"
fi
done
And here's the error:
bash: [0%: command not found
Host down
bash: [100%: command not found
Host down
My purpose is to make a ping sweep program which scans the range 192.168.1.1-255 and it notifies the host's status. I know about nmap but just wanted to learn skills in Bash so I made this one. Please try to tell what the error meant. I mean to what command it's referring "command not found"?
The ping command returns error code if there was any problem, so you do not need to parse the output:
for i in {1..255}
do
if ping -c1 -W1 -n "192.168.1.$i"
then
echo 'Host live'
else
echo 'Host down'
fi
done
Primary diagnosis
The [ command needs a space after its name, just like the rm command needs a space after its name and the ls command does, and … The [ command also requires its last argument to be ], spelled thus, so there needs to be a space before that, too.
You have:
if ["$(ping -c1 -W1 -n 192.168.1.$i | grep '%' | cut -d',' -f3 | cut -d' ' -f2)" -eq "0%"]
At minimum, you need:
if [ "$(ping -c1 -W1 -n 192.168.1.$i | grep '%' | cut -d',' -f3 | cut -d' ' -f2)" -eq "0%" ]
Secondary issues
Note that 'at minimum' means, amongst other things, that I've not spent time analyzing why you are executing the complex sequence of 4 commands in the test condition, or looked for ways to cut that down to two (using grep and cut twice suggests that sed or a more powerful tool would be better). I griped about the formatting in the original version of the question, where the loop (it isn't a nested loop, incidentally — or it isn't in the code shown) was all on one line thanks to Bash flattening it in history. My version of the code would have far fewer semicolons in it, for example. The -eq operator in [ is for testing the equality of numbers (the converse convention applies in Perl, where eq is for testing strings and == tests numbers). Note that POSIX standard [ (aka test) does not support == as a synonym for =, though Bash does. It isn't entirely clear that "0%" is OK as an argument for numeric comparison. Many programs would not object — the zero can be converted and the residue doesn't matter; others might decide legitimately to complain that the whole string could not be converted, so it is erroneous. Careful code wouldn't risk the disconnect.
See Steven Penny's answer for a more thorough rewrite of the code. My answer remains a valid diagnosis of the immediate problem of not being able to find commands named [0% and [100%.
Related
I'm trying to create a bash script from Georgia Wiedmann's book. I have my XP target machine and my Kali machine up and running.
#!/bin/bash
if [ "$1" == "" ]
then
echo "Usage: ./pingscript.sh [network]"
echo "example: ./pingscript.sh 192.168.x.x"
else
for x in 'seq 1 254'; do
ping -c 1 $1.$x | grep "64 bytes" | cut -d" " -f4 | sed 's/.$//'
done
fi
I don't know whether the 8.8.8.8 should be my XP's IP or Gateway address but when I do ./pingscript.sh 192.168.x.x I should be getting a response but it instead says Ping unknown host.
Anyone help?
Here's shellcheck:
Line 7:
for x in 'seq 1 254'; do
^-- SC2041: This is a literal string. To run as a command, use $(..) instead of '..' .
Quoting its wiki:
The intent was to run the code in the single quotes. This would have worked with slanted backticks, `..`, but here the very similar looking single quotes '..' were used, resulting in a string literal instead of command output.
This is one of the many problems with backticks, so it's better to use $(..) to expand commands.
In other words, use:
for x in $(seq 1 254); do
I am new to shell script , i want to write a script to monitor CPU usage and if the CPU usage reaches a threshold it should print the CPU usage by top command ,here is my script , which is giving me error bad number and also not storing any value in the log files
while sleep 1;do if [ "$(top -n1 | grep -i ^cpu | awk '{print $2}')">>sy.log - ge "$Threshold" ]; then echo "$(top -n1)">>sys.log;fi;done
Your script HAS to be indented and stored to a file, especially if you are new to shell !
#!/bin/sh
while sleep 1
do
if [ "$(top -n1 | grep -i ^cpu | awk '{print $2}')">>sy.log - ge "$Threshold" ]
then
echo "$(top -n1)" >> sys.log
fi
done
Your condition looks a bit odd. It may work, but it looks really complex. Store intermediate results in variables, and evaluate them.
Then, you will immediately see the syntax error on the “-ge”.
You HAVE to store logfiles within an absolute path for security reasons. Use variables to simplify the reading.
#!/bin/sh
LOGFILE=/absolute_path/sy.log
WHOLEFILE=/absolute_path/sys.log
Thresold=80
while sleep 1
do
TOP="$(top -n1)"
CPU="$(echo $TOP | grep -i ^cpu | awk '{print $2}')"
echo $CPU >> $LOGFILE
if [ "$CPU" -ge "$Threshold" ] ; then
echo "$TOP" >> $WHOLEFILE
fi
done
You have a couple of errors.
If you write output to sy.log with a redirection then that output is no longer available to the shell. You can work around this with tee.
The dash before -ge must not be followed by a space.
Also, a few stylistic remarks:
grep x | awk '{y}' is a useless use of grep; this can usefully and more economically (as well as more elegantly) be rewritten as awk '/x/{y}'
echo "$(command)" is a useless use of echo -- not a deal-breaker, but you simply want command; there is no need to capture what it prints to standard output just so you can print that text to standard output.
If you are going to capture the output of top -n 1 anyway, there is no need really to run it twice.
Further notes:
If you know the capitalization of the field you want to extract, maybe you don't need to search case-insensitively. (I could not find a version of top which prints a CPU prefix with the load in the second field -- it the expression really correct?)
The shell only supports integer arithmetic. Is this a bug? Maybe you want to use Awk (which has floating-point support) to perform the comparison? This also allows for a moderately tricky refactoring. We make Awk output an exit code of 1 if the comparison fails, and use that as the condition for the if.
#!/bin/sh
while sleep 1
do
if top=$(top -n 1 |
awk -v thres="$Threshold" '1; # print every line
tolower($1) ~ /^cpu/ { print $2 >>"sy.log";
exitcode = ($2 >= thres ? 0 : 1) }
END { exit exitcode }')
then
echo "$top" >>sys.log
fi
done
Do you really mean to have two log files with nearly the same name, or is that a typo? Including a time stamp in the log might be useful both for troubleshooting and for actually using the log files.
I've used the column command to split some of my output into 3 different columns. Problem is with the final column, the filetype output is being split into a 4th and 5th column because of the spaces.
Can somebody tell me how to change my code so that output stays under the Filetype column?
list_files()
{
if [ "$(ls -A ~/.junkdir)" ]
then
filesdir=/home/student/.junkdir/*
echo "Listing files in Junk Directory"
output="FILENAME SIZE(BYTES) TYPE \n\n---------------- ---------------- ------------------- "
for listed_file in $filesdir
do
file_name=$(basename "file $listed_file" | cut -d ' ' -f1)
file_size=$(du --bytes $listed_file | awk '{print $1}')
file_type=$(file $listed_file | cut -d ' ' -f2-)
output="$output\n${file_name} ${file_size} ${file_type}\n"
done
echo -ne $output | column -t
else
echo 'Junk directory is empty'
fi
}
The output at the moment..
Listing files in Junk Directory
FILENAME SIZE(BYTES) TYPE
---------------- ---------------- -------------------
files.txt 216 ASCII text
forLoop 401 Bourne-Again shell script,
ASCII text executable
I rarely give full solution, but it seems you are really stuck.
list_files2()
{
filesdir=/home/student/.junkdir/*
printf "FILENAME\1SIZE(BYTES)\1TYPE\1\n\n----------------\1----------------\1-------------------\n"
for listed_file in $filesdir
do
file_name=$(basename "file $listed_file" | cut -d ' ' -f1)
file_size=$(du --bytes $listed_file | awk '{print $1}')
file_type=$(file $listed_file | cut -d ' ' -f2-)
printf "%s\1%s\1%s\n" "${file_name}" "${file_size}" "${file_type}"
done
}
list_files()
{
if [ "$(ls -A ~/.junkdir)" ]
then
echo "Listing files in Junk Directory"
list_files2 | column -t -s $'\1'
else
echo 'Junk directory is empty'
fi
}
I slightly reorganized your code and made some other changes as well. I will explain what I did.
$'\1' is the 0x01 char. Even though I proposed to use $'\0', it's weird that my version of column has weird interaction with it appearing in the input. But in shell scripting practice, it's generally a bad idea to assume blank separator. In your case, you got caught by space, which is reasonable, because white space has so much overloaded meaning, you cannot prevent it from appearing in a human readable text. The solution to this is to consider using exotic chars like 0x00 or 0x01 as separator instead, which is almost always the case that it won't show up as a part of the text. So it's very safe to use and in fact, it's common in portable shell scripting to use 0x00 as separator.
Do not concatenate string like you did. In fact, there are couple problems with it.
one is you keep concatenating string while you don't really need the intermediate result.
another biteback is what if inside of your text, strings like \n exist and it should be interpreted as literal? echo -e is not going to distinguish that. yet another SO question on the road.
using printf in fact is more flavorable in shell, though I use echo a lot myself as well. Here the benefit of using printf is evident.
I don't have your files so I didn't try it, though I would expect it works. Let me know if there're glitches here and there.
Perhaps you can try
output="$output\n${file_name}\t${file_size}\t${file_type}\n"
...
echo -ne $output
The task requires that a bash script be written that will search the "who" command for a given user ID which will be provided via command line argument
This script will display whether or not this user ID is logged in
So far I know that to get the user ID, one can do:
who | cut -d' ' -f1 | grep "userIdToSearchFor"
This grep will display the user ID if it exists, or nothing if it doesn't, so it seems like a good method
I believe the $1 variable will hold the first command line argument
How can I implement this in a bash script file please?
EDIT:
Current working script looks like this
#!/bin/bash
userid=$(who | cut -d' ' -f1 | grep "$1")
if [ "$1" == "$userid" ]
then
echo "online"
else
echo "offline"
fi
This should work for you :
STRING=$(who | cut -d' ' -f1 | grep "$1")
if [ "$1" = "$STRING" ]
then
echo "online"
else
echo "offline"
fi
Some comments and suggestions :
No spaces on both sides of the = when you assign variables (that's where your error message come from).
To assign commands result to a variable, you must use the $( ) syntax. See command substitution for more.
Quote you vars in your test to prevent word splitting.
You should loop on the test, there could be multiple identical usernames.
Avoid caps in you variable names not to confuse with environment variables which are capitalized by convention.
Avoid to use the type of the var for its name, in your case username would be a better choice.
You're doing it the hard way.
$ cat user.sh
#!/bin/bash
# user.sh username - shows whether username is logged on or not
if who | grep --silent "^$1 " ; then
echo online
else
echo offline
fi
$ ./user.sh msw
online
SSH from Host A to a few hosts (only one listed below right now) using the SSH Key I generated and then go to a specific file, grep for a specific word with a date of yesterday .. then I want to email this output to myself.
It is sending an email but it is giving me the command as opposed to the output from the command.
#!/bin/bash
HOST="XXXXXXXXXXXXXXXXXX, XXXXXXXXXXXXX"
DATE=$(date -d "yesterday")
INVALID=' cat /xxx/xxx/xxxxx | grep 'WORD' | sed 's/$/.\n/g' | grep "$DATE"'
COUNT=$(echo "$INVALID" | wc -c)
for x in $HOSTS
do
ssh BLA#"$x" $COUNT
if [ "$COUNT" -gt 1 ];
then
EMAILTEXT=""
if [ "$COUNT" -gt 1 ];
then
EMAILTEXT="$INVALID"
fi
fi
done | echo -e "$EMAILTEXT" | mail XXXXXXXXXXX.com
This isn't properly an attempt to answer your question, but I think you should be aware of some fundamental problems with your code.
INVALID=' cat /xxx/xxx/xxxxx | grep 'WORD' | sed 's/$/.\n/g' | grep "$DATE"'
This assigns a simple string to the variable INVALID. Because of quoting issues, s/$/.\n/g is not quoted at all, and will probably be mangled by the shell. (You cannot nest single quotes -- the first single-quoted string extends from the first quote to the next one, and then WORD is outside of any quotes, followed by the next single-quoted string, etc.)
If your intent is to execute this as a command at this point, you are looking for a command substitution; with the multiple layers of uselessness peeled off, perhaps something like
INVALID=$(sed -n -e '/WORD/!d' -e "/$DATE/s/$/./p" /xxx/xxx/xxxx)
which looks for a line matching WORD and $DATE and prints the match with a dot appended at the end -- I believe that's what your code boils down to, but without further insights into what this code is supposed to do, it's impossible to tell if this is what you actually need.
COUNT=$(echo "$INVALID" | wc -c)
This assigns a number to $COUNT. With your static definition of INVALID, the number will always be 62; but I guess that's not actually what you want here.
for x in $HOSTS
do
ssh BLA#"$x" $COUNT
This attempts to execute that number as a command on a number of remote hosts (except the loop is over HOSTS and the variable containing the hosts is named just HOST). This cannot possibly be useful, unless you have a battery of commands named as natural numbers which do something useful on these remote hosts; but I think it's safe to assume that that is not what is supposed to be going on here (and if it was, it would absolutely be necessary to explain this in your question).
if [ "$COUNT" -gt 1 ];
then
EMAILTEXT=""
if [ "$COUNT" -gt 1 ];
then
EMAILTEXT="$INVALID"
fi
fi
So EMAILTEXT is either an empty string or the value of INVALID. You assigned it to be a static string above, which is probably the source of your immediate question. But even if it was somehow assigned to a command on the local host, why do you need to visit remote hosts and execute something there? Or is your intent actually to execute the command on each remote host and obtain the output?
done | echo -e "$EMAILTEXT" | mail XXXXXXXXXXX.com
Piping into echo makes no sense at all, because it does not read its standard input. You should probably just have a newline after done; though a possibly more useful arrangement would be to have your loop produce output which we then pipe to mail.
Purely speculatively, perhaps something like the following is what you actually want.
for host in $HOSTS; do
ssh BLA#"$host" sed -n -e '/WORD/!d' -e "/$DATE/s/$/./p" /xxx/xxx/xxxx |
grep . || echo INVALID
done | mail XXXXXXXXXXX.com
If you want to check that there is strictly more than one line of output (which is what the -gt 1 suggests) then this may need to be a little bit more complicated.
Your command substitution is not working. You should read up on how it works but here are the problem lines:
COUNT=$(echo "$INVALID" | wc -c)
[...]
ssh BLA#"$x" $COUNT
should be:
COUNT_CMD="'${INVALID} | wc -c'"
[...]
COUNT=$(ssh BLA#"$x" $COUNT_CMD)
This inserts the value of $INVALID into the string, and puts the whole thing in single quotes. The single quotes are necessary for the ssh call so the pipes aren't evaluated in the script but on the remote host. (COUNT is changed to COUNT_CMD for readability/clarity.)
EDIT:
I misread the question and have corrected my answer.