I am looking for a simpler, more idiomatic and most importantly standards (POSIX) compliant way to reverse an IP address, using sh the Unix shell.
Here's my current solution:
RevIP() {
echo "$1"|tr . "\n"|tac|tr "\n" .
# 'Split' on the dot character, reverse the list, 'join' with dot
}
Example usage:
$ RevIP 23.45.67.89
89.67.45.23.
Issues:
this uses tac which is not in POSIX
the output ends in . and there's no newline. Not a major problem but ideally it should end in \n instead.
This could be solved by an additional |sed s/... at the end but is there a way to do this more elegantly so there's no need for that?
One doesn't need external commands for this; shell builtins suffice.
reversed=$(echo "$ip" | { IFS=. read q1 q2 q3 q4; echo "$q4.$q3.$q2.$q1"; })
...or, a little more efficiently (but a little less tersely):
IFS=. read q1 q2 q3 q4 <<EOF
$ip
EOF
reversed="$q4.$q3.$q2.$q1"
this should be one possibility for what you're looking
#!/bin/sh
ip="$1"
reversed=$(echo "$ip" | awk -F '.' '{print $4 "." $3 "." $2 "." $1}')
echo "$reversed"
$ echo '23.45.67.89' |
> mawk '$!NF = sprintf((_ = "%s.%s") "." _,
> $(_ = NF), $--_, $--_, $--_)' FS='[.]'
89.67.45.23
Related
i am passing a argument and that argument i have to match in file and extract the information. Could you please how I can get it?
Example:
I have below details in file-
iMedical_Refined_load_Procs_task_id=970113
HV_Rawlayer_Execution_Process=988835
iMedical_HV_Refined_Load=988836
DHS_RawLayer_Execution_Process=988833
iMedical_DHS_Refined_Load=988834
If I am passing 'hv' as argument so it should to pick 'iMedical_HV_Refined_Load' and give the result - '988836'
If I am passing 'dhs' so it should pick - 'iMedical_DHS_Refined_Load' and give the result = '988834'
I tried below logic but its not giving the result correctly. What Changes I need to do-
echo $1 | tr a-z A-Z
g=${1^^}
echo $g
echo $1
val=$(awk -F= -v s="$g" '$g ~ s{print $2}' /medaff/Scripts/Aggrify/sltconfig.cfg)
echo "TASK ID is $val"
Assuming your matching criteria is the first string after delimiter _ and the output needed is the numbers after the = char, then you can try this sed
$ sed -n "/_$1/I{s/[^=]*=\(.*\)/\1/p}" input_file
$ read -r input
hv
$ sed -n "/_$input/I{s/[^=]*=\(.*\)/\1/p}" input_file
988836
$ read -r input
dhs
$ sed -n "/_$input/I{s/[^=]*=\(.*\)/\1/p}" input_file
988834
If I'm reading it right, 2 quick versions -
$: cat 1
awk -F= -v s="_${1^^}_" '$1~s{print $2}' file
$: cat 2
sed -En "/_${1^^}_/{s/^.*=//;p;}" file
Both basically the same logic.
In pure bash -
$: cat 3
while IFS='=' read key val; do [[ "$key" =~ "_${1^^}_" ]] && echo "$val"; done < file
That's a lot less efficient, though.
If you know for sure there will be only one hit, all these could be improved a bit by short-circuit exits, but on such a small sample it won't matter at all. If you have a larger dataset to read, then I strongly suggest you formalize your specs better than "in this set I should get...".
I want to evaluate the expression and display the output correct to 3 decimal places i tried with below code but it is not working help me how to do that in bash.
echo -e "Enter expression to calculate : \c"
read num
let a=num
printf '%f\n' "$a"
Input : 5+50*3/20 + (19*2)/7
Output : 17.000000
Desired Output : 17.929
With bc:
echo 'scale=3; 5+50*3/20 + (19*2)/7' | bc -l
Output:
17.928
Instead of let a=num, you could for example:
echo $num | bc
17.92857142857142857142
This is one of the very rare cases where it's acceptable to let a shell variable expand to become part of the body of an awk script:
$ num='5+50*3/20 + (19*2)/7'
$ awk 'BEGIN{print '"$num"'}'
17.9286
$ awk 'BEGIN{printf "%0.3f\n", '"$num"'}'
17.929
I have lot of file which I need to concatenate together with same prefix. I have an idea, but I do not know how to solve this problem:
files:
NAME1_C001_xxx.tsv
NAME1_C001_yyy.tsv
NAME2_C001_xxx.tsv
NAME2_C001_yyy.tsv
I want to print just uniq prefix - NAME1 and NAME2. Length of string in prefix and suffix is vary, but always before prefix is _C001
my solution is:
fo i in *.tsv
do prexix=$(printf "%s\n" "${i%_C001*}")
cat $prefix_C001_xxx.tsv $prefix_C001_yyy.tsv > ${i%_C001*}.merged.tsv
done;
But this solution is not very good. I have each prefix twice.
Thank you for any help.
EDITED:
One solution thanks to anubhava:
fo i in $(printf "%s\n" *.tsv | awk -F '_C001' '!seen[$1]++{print $1}')
do
cat $prefix_C001_xxx.tsv $prefix_C001_yyy.tsv > ${i%_C001*}.merged.tsv
done;
You don't need printf at all here; it's just an unnecessary wrapper around the parameter substitution you are already using.
for i in *.tsv
do prefix=${i%_C001*}
[[ -f $prefix.merged.tsv ]] && continue # Avoid doing the same prefix twice
cat "${prefix}"_* > "$prefix.merged.tsv"
done
As your filenames don't contain any newline you can pipe your list to a awk command to print unique prefixes using field separator as _C001:
printf "%s\n" *.tsv | awk -F '_C001' '!seen[$1]++{print $1}'
NAME1
NAME2
You can also use _ as FS in awk:
printf "%s\n" *.tsv | awk -F _ '!seen[$1]++{print $1}'
actlist file contains around 15 records. I want to print/store each row in a variable to perform further action. script runs but echo $j displays blank value. What is the issue?
my script:
#/usr/bin/sh
acList=/root/john/actlist
Rowcount=`wc -l $acList | awk -F " " '{print $1}'`
for ((i=1; i<=Rowcount; i++)); do
j=`awk 'FNR == $i{print}' $acList`
echo $j
done
file: actlist
cat > actlist
5663233332 2223 2
5656556655 5545 5
4454222121 5555 5
.
.
.
The issue happens to be related to quotes and to the way the shell interpolates variables.
More specifically, when you write
j=`awk "FNR == $i{print}" $acList`
the AWK code must be enclosed into double quotes. This is necessary if you want the shell to be able to substitute the $i with the actual value stored in the i variable.
On the other hand, if you write
j=`awk 'FNR == $i{print}' $acList`
i.e. with single quotes, the $i will be interpreted as a literal string.
Hence the fixed code will read:
#/usr/bin/sh
acList=/root/john/actlist
Rowcount=`wc -l $acList | awk -F " " '{print $1}'`
for ((i=1; i<=Rowcount; i++)); do
j=`awk "FNR == $i{print}" $acList`
echo $j
done
Remember: it is always the shell that does variable interpolation before calling other commands.
Having said that, there are some places, in supplied code, where some improvements could be devised. But that's another story.
Unfortunately all your script does is print the contents of the input file so we can't help you figure out the right approach to do whatever it is you REALLY want to do without more information on what that is but chances are this is the right starting point:
acList=/root/john/actlist
awk '
{ print }
' "$acList"
I think you would probably be better off with this for parsing your file:
#!/bin/bash
while read a b c; do
echo $a, $b, $c
done < "$actlist"
Output:
5663233332, 2223, 2
5656556655, 5545, 5
4454222121, 5555, 5
Updated
Whilst the above demonstrates the concept I was suggesting, as #EdMorton rightly says in the comments section, the following code would be more robust for a production environment.
#!/bin/bash
while IFS= read -r a b c; do
echo "$a, $b, $c"
done < "$actlist"
I have a string variable in my script, made up of the 9 permission characters from ls -l
eg:
rwxr-xr--
I want to manipulate it so that it displays like this:
r w x r - x r - -
IE every three characters is tab separated and all others are separated by a space. The closest I've come is using a printf
printf "%c %c %c\t%c %c %c\t%c %c %c\t/\n" "$output"{1..9}
This only prints the first character but formatted correctly
I'm sure there's a way to do it using "sed" that I can't think of
Any advice?
Using the Posix-specified utilities fold and paste, split the string into individual characters, and then interleave a series of delimiters:
fold -w1 <<<"$str" | paste -sd' \t'
$ sed -r 's/(.)(.)(.)/\1 \2 \3\t/g' <<< "$output"
r w x r - x r - -
Sadly, this leaves a trailing tab in the output. If you don't want that, use:
$ sed -r 's/(.)(.)(.)/\1 \2 \3\t/g; s/\t$//' <<< "$str"
r w x r - x r - -
Why do u need to parse them? U can access to every element of string by copy needed element. It's a very easy and without any utility, for example:
DATA="rwxr-xr--"
while [ $i -lt ${#DATA} ]; do
echo ${DATA:$i:1}
i=$(( i+1 ))
done
With awk:
$ echo "rwxr-xr--" | awk '{gsub(/./,"& ");gsub(/. . . /,"&\t")}1'
r w x r - x r - -
> echo "rwxr-xr--" | sed 's/\(.\{3,3\}\)/\1\t/g;s/\([^\t]\)/\1 /g;s/\s*$//g'
r w x r - x r - -
( Evidently I didn't put much thought into my sed command. John Kugelman's version is obviously much clearer and more concise. )
Edit: I wholeheartedly agree with triplee's comment though. Don't waste your time trying to parse ls output. I did that for a long time before I figured out you can get exactly what you want (and only what you want) much easier by using stat. For example:
> stat -c %a foo.bar # Equivalent to stat --format %a
0754
The -c %a tells stat to output the access rights of the specified file, in octal. And that's all it prints out, thus eliminating the need to do wacky stuff like ls foo.bar | awk '{print $1}', etc.
So for instance you could do stuff like:
GROUP_READ_PERMS=040
perms=$(stat -c %a foo.bar)
if (( (perms & GROUP_READ_PERMS) != 0 )); then
... # Do some stuff
fi
Sure as heck beats parsing strings like "rwxr-xr--"
sed 's/.../& /2g;s/./& /g' YourFile
in 2 simple step
A version which includes a pure bash version for short strings, and sed for longer strings, and preserves newlines (adding a space after them too)
if [ "${OS-}" = "Windows_NT" ]; then
threshold=1000
else
threshold=100
fi
function escape()
{
local out=''
local -i i=0
local str="${1}"
if [ "${#str}" -gt "${threshold}" ]; then
# Faster after sed is started
sed '# Read all lines into one buffer
:combine
$bdone
N
bcombine
:done
s/./& /g' <<< "${str}"
else
# Slower, but no process to load, so faster for short strings. On windows
# this can be a big deal
while (( i < ${#str} )); do
out+="${str:$i:1} "
i+=1
done
echo "$out"
fi
}
Explanation of sed. "If this is the last line, jump to :done, else append Next into buffer and jump to :combine. After :done is a simple sed replacement expression. The entire string (newlines and all) are in one buffer so that the replace works on newlines too (which are lost in some of the awk -F examples)
Plus this is Linux, Mac, and Git for Windows compatible.
Setting awk -F '' allows each character to be bounded, then you'll want to loop through and print each field.
Example:
ls -l | sed -n 2p | awk -F '' '{for(i=1;i<=NF;i++){printf " %s ",$i;}}'; echo ""
The part seems like the answer to your question:
awk -F '' '{for(i=1;i<=NF;i++){printf " %s ",$i;}}'
I realize, this doesn't provide the trinary grouping you wanted though. hmmm...