This question already has answers here:
How do I pipe a file line by line into multiple read variables?
(3 answers)
Closed 18 days ago.
I want to use multiple variable in for loop at once in sh.
I have a query like this:
top -n 1 -b -c| awk -vOFS="\t" '{print $1,$2,$9}'
I know i use for loop in bash like this:
for i in {2..10}
do
echo "output: $i"
done
what i want to try is:
for x y z in $(top -n 1 -b -c| awk -vOFS="\t" {print $1,$2,$9}')
do
echo "output: $x $y $z"
done
Pipe to a while read loop:
top -n 1 -b -c| awk -vOFS="\t" '{print $1,$2,$9}' | while IFS=$'\t' read -r x y z
do
echo "output: $x $y $z"
done
Related
This question already has answers here:
How do I set a variable to the output of a command in Bash?
(15 answers)
Closed 4 years ago.
the variables line,word,char dont get value!
line= wc -l < $*
word= wc -w < $*
char= wc -m < $*
echo "Number of characters in test.txt is $char"
echo "Number of words in test.txt is $word"
echo "Number of lines in test.txt is $line"
You have to wrap the command in $():
line=$(wc -l < $1)
This question already has answers here:
unix sed substitute nth occurence misfunction?
(3 answers)
Closed 4 years ago.
In bash, suppose I have the input:
ATGTGSDTST
and I want to print:
AT
ATGT
ATGTGSDT
ATGTGSDTST
which means that I need to look for all the substrings that end with 'T' and print them.
I thought I should use sed inside a for loop, but I don't understand how to use sed correctly in this case.
Any help?
Thanks
The following script uses sed:
#!/usr/bin/env bash
pattern="ATGTGSDTST"
sub="T"
# Get number of T in $pattern:
num=$(grep -o -n "T" <<< "$pattern" | cut -d: -f1 | uniq -c | grep -o "[0-9]\+ ")
i=1
text=$(sed -n "s/T.*/T/p" <<< "$pattern")
echo $text
while [ $i -lt $num ]; do
text=$(sed -n "s/\($sub[^T]\+T\).*/\1/p" <<< "$pattern")
sub=$text
echo $text
((i++))
done
gives output:
AT
ATGT
ATGTGSDT
ATGTGSDTST
No sed needed, just use parameter expansion:
#! /bin/bash
string=ATGTGSDTST
length=${#string}
prefix=''
while (( ${#prefix} != $length )) ; do
sub=${string%%T*}
sub+=T
echo $prefix$sub
string=${string#$sub}
prefix+=$sub
done
This question already has answers here:
"echo -n" prints "-n"
(11 answers)
Closed 6 years ago.
#!/bin/bash
echo "Enter process name"
read process
if pgrep "$process" > /dev/null
then
echo 0 $(awk '/Rss/ {print "+", $2}' /proc/`pidof $process`/smaps) | bc;
echo "Kb"
else
echo "Process $process not running"
fi
The output of the code above is
41250
Kb
and I need the "Kb" output in the same line as the number like this
41250 Kb
You can use echo -n to output data without a trailing newline but, for this particular case, awk is perfectly capable of doing arithmetic and formatting on its own, without involving bc or unnecessary sub-processes:
awk '/Rss/ {sum += $2} END {print sum" Kb"}' /proc/`pidof $process`/smaps
You can see that in the following transcript which adds up the two Rss figures 75 and 11 to get 86:
pax> printf Rss 75\nCss 22\nRss 11\n' | awk '/Rss/ {sum += $2} END {print sum" Kb"}'
86 Kb
Use the -n Flag.
Example:
echo -n 'I do not want a new line,'
echo ' because there is something else here.'
Use $ man echo to get more information.
The newline after 41250 was actually from bc, not echo.
Capturing output of bc in a variable removes trailing newlines (ref).
#!/bin/bash
kbCount=$( echo "1+2" | bc)
echo $kbCount "Kb"
Now you should be able to fix it :)
This question already has answers here:
Bash tool to get nth line from a file
(22 answers)
Closed 7 years ago.
This is my script. It print every row in the file with the number of row.
Next i want to read which row user choosed and save it to some variable.
I=1
for ROW in $(cat file.txt)
do
echo "$I $ROW"
I=`expr $I + 1`
done
read var
awk 'FNR = $var {print}' file.txt
Then i want to to print / save the chosen row into the file.
How can I do this ?
when i echo $var it shows me properly the number. But when i'm trying to use this variable in awk, it print every line.
How to read the 'var' line from file?
And moreover, how to save this line in other variable?
Example file.txt
1 line1
2 line2
3 line3
4 line4
when i tap 3 i want to read third line from file.
Try this:
cat -n file.txt; read var; line="$(sed -n ${var}p file)"; echo "$line"
With more focus on Dryingsoussage's version:
#!/bin/bash
file="file.txt"
declare -i counter=0 # set integer attribute
var=0
while read -r line; do
counter=counter+1
printf "%d %s\n" "$counter" "$line"
done < "$file"
# check for number and greater-than 0 and less-than-or-equal $counter
until [[ $var =~ ^[0-9]+$ ]] && [[ $var -gt 0 ]] && [[ $var -le $counter ]]; do
read -p "Enter line number:" var
done
awk -v var="$var" 'FNR==var {print}' "$file"
You cannot use $varname inside ' ' they will not be resolved.
look at this other post it should help you:
How to use shell variables in an awk script
cat -n file.txt
read var
row="$(awk -v tgt="$var" 'NR==tgt{print;exit}' file.txt)"
First: You cannot use $var in a single quotes, as echo '$var' would be plain $var, no its value.
Second: You used = (assignment) operator instead of == (equality) operator.
Third: You don't have to write { print } if you want the line to be printed. You can write nothing instead.
Fourth: As was explained in the deleted comment below - do not allow bash expanding the variables in the awk script code, as it can lead to code injection.
So conclusion is:
awk -v var="$var" 'FNR == var' file.txt
should do what you want.
This is what i have done to perform this function but I am not getting what i want.
#!/bin/sh
DIRECTIONPART1=4-7-9
for (( i=1; i<=3; i++ ))
do
x=`echo $DIRECTIONPART1| awk -F'-' '{print $i}'`
myarray[$i]=$x
done
for (( c=1; c<=3; c++ ))
do
echo ${myarray[$c]}
done
Problem we realised at this step
x=`echo $DIRECTIONPART1| awk -F'-' '{print $i}'`
Please help me in getting the result
This is what i get :
4-7-9
4-7-9
4-7-9
But I want this:
4
7
9
you are right with line of problem. The problem is that you cant use $i as variable in print. I have tried little workaround which worked for me:
x=`echo $DIRECTIONPART1| awk -F '-' -v var=$i '{print $var }'`
in all it looks like:
#!/bin/sh
DIRECTIONPART1=4-7-9
for (( i=1; i<=3; i++ ))
do
x=`echo $DIRECTIONPART1| awk -F '-' -v var=$i '{print $var }'`
myarray[$i]=$x
done
for (( c=1; c<=3; c++ ))
do
echo ${myarray[$c]}
done
with expected output:
# sh test.sh
4
7
9
#
The simplest portable way to get the desired output is to use $IFS (in a subshell):
#!/bin/sh
DIRECTIONPART1=4-7-9
(IFS=- && echo $DIRECTIONPART1)
The shell array would not work portably, as POSIX, ksh, and bash do not
agree on arrays. POSIX doesn't have any; ksh and bash use different syntax.
If you really want an array, I would suggest to do the entire thing in awk:
#!/bin/sh
DIRECTIONPART1=4-7-9
awk -v v=${DIRECTIONPART1} 'BEGIN {
n=split(v,a,"-")
for (i=1;i<=n;i++) {
print a[i]
}
}'
This will produce one line for each value in the string:
4
7
9
And if you want bash arrays, drop the #!/bin/sh, and do something like this:
#!/bin/bash
DIRECTIONPART1=4-7-9
A=( $(IFS=- && echo $DIRECTIONPART1) )
for ((i=0;i<=${#A[#]};i++))
do
echo ${A[i]}
done
Calling awk multiple times, or even once, is not the right thing to do. Use the bash built-in read to populate the array.
# Note that the quotes here are only necessary to
# work around a bug that was fixed in bash 4.3. It
# doesn't hurt to use them in any version, though.
$ IFS=- read -a myarray <<< "$DIRECTIONPART_1"
$ printf '%s\n' "${myarray[#]}"
4
7
9
[akshay#localhost tmp]$ bash test.sh
#!/usr/bin/env bash
DIRECTIONPART1=4-7-9
# Create array
IFS='-' read -a array <<< "$DIRECTIONPART1"
#To access an individual element:
echo "${array[0]}"
#To iterate over the elements:
for element in "${array[#]}"
do
echo "$element"
done
#To get both the index and the value:
for index in "${!array[#]}"
do
echo "$index ${array[index]}"
done
Output
[akshay#localhost tmp]$ bash test.sh
4
4
7
9
0 4
1 7
2 9
OR
[akshay#localhost tmp]$ cat test1.sh
#!/usr/bin/env bash
DIRECTIONPART1=4-7-9
array=(${DIRECTIONPART1//-/ })
for index in "${!array[#]}"
do
echo "$index ${array[index]}"
done
Output
[akshay#localhost tmp]$ bash test1.sh
0 4
1 7
2 9