The arithmetic tag has no wiki summary.
16
votes
5answers
1k views
Parenthesis in bash arithmetic: 3 * (2 + 1)
expr does not seem to like parenthesis (used in mathematics to explicit operator priority):
expr 3 * (2 + 1)
bash: syntax error near unexpected token `('
How to express operator priority in bash?
0
votes
4answers
202 views
Bash if conditions of variables within intervals
I have some data spread over time intervals, and I want to take some of those data within the time intervals. For example, I have data at times within 1..9, 11..19, etc., and I want to take data ...
1
vote
4answers
238 views
Error: integer expression expected
I have written a script to determine the Load average on the server as follows:
#!/bin/bash
loadavg=`top -b -n1 | grep -i load | awk -F, '{print$4}'| awk -F: '{print $2}'`
if [ "${loadavg}" -le 1 ...
2
votes
2answers
516 views
Comparison of decimal numbers in bash
My search this morning was about how could I compare two decimal numbers in bash, and I came to this answser: How to compare to floating point number in a shell script. This one, however, doesn't ...
4
votes
2answers
1k views
Bash's conditional operator and assignment
Can we use bash's conditional operator with assignment operators after colon?
Bash reference manual explains the arithmetic operators as follows.
conditional operator expr ? expr : expr
assignment ...
1
vote
1answer
432 views
Divide a variable by a number? [duplicate]
Basically I need to convert centimetres to inches which I am trying to do by diving the area in centimetres by 2.54.
But I just cannot get this to work.
echo "please enter width and then height"
...
6
votes
4answers
3k views
Check if $REPLY is in a range of numbers
I'm writing a shell script for Linux, using Bash, to translate any video-file into a MP4. For that, I'm using avconv with libvorbis for audio.
Inside my script, I have a question for the user :
...
6
votes
1answer
270 views
What is the rationale for the bash shell not warning you of arithmetic overflow etc.?
There are limits set for the arithmetic evaluation capabilities of the bash shell. The manual is succinct about this aspect of shell arithmetic but states:
Evaluation is done in fixed-width ...
6
votes
3answers
112 views
Is it possible to use variables in count braces in Bash?
I'm searching for a solution to a Bash 4 problem I have.
Bash 4 is able to iterate with leading zeros.
For the line:
for i in {001..005}; do echo -n $i" ";done;echo
the output is
001 002 003 004 ...
3
votes
2answers
202 views
Unit multiplier conversion in a shell script
I need to convert human-readable sizes into bytes. Unfortunately numfmt function is not accessible for me. Is there any other alternative? I need a shell/bash function to call from inside the sh ...
0
votes
1answer
44 views
TCSH bitwise | operator
How do I use the bitwise logical-or operator, |, in tcsh?
I enter
@ y = 1001; @ z = 0110;
@ x = $y|$z
110: Command not found.
1
vote
2answers
98 views
modify user-defined System Variables(that is a number) of remote Server machine using ssh?
I want to modify the value of a System Variable of a remote server .
The IP of server is 172.16.22.53.
The server runs Windows OS,and Cygwin instlled in it.In ...
2
votes
2answers
586 views
Remove scientific notation bash script
When I convert MB to GB I'm getting below output. I want this output in normal format. When I use bc I'm getting an error. The text file contains nearly 100 such lines like this.
I want to print this ...
2
votes
3answers
78 views
Change value of a strings representing number
I have the following expression :
a="2013"
How can I change the value of a to "2012".
4
votes
3answers
611 views
How do I create a bash script that sums any number of command line arguments?
How would I create a bash script that the user can use to sum any amount of command line arguments? For example, say my script is called sum:
sum 3
3
sum 3 5
8
sum 9 8 21
38
And so on.. I ...
2
votes
4answers
701 views
how to convert number to time format in shell script?
I want to cut a video into about 10 minute parts like this.
ffmpeg -i video.mp4 -ss 00:00:00 -t 00:10:00 -c copy 01.mp4
ffmpeg -i video.mp4 -ss 00:10:00 -t 00:10:00 -c copy 02.mp4
ffmpeg -i video.mp4 ...
1
vote
3answers
2k views
Shell scripting to divide numbers inside a file
I have a single column and 12 rows. Each row has numerical values. I want to divide each row values by some constant number (say C) using shell (bash) scripting. How to do this ?
Thanks in advance..
9
votes
3answers
841 views
Why does “$(( ~33 ))” produce -34?
$ echo $(( 255 ))
255
$ echo $(( 33 ))
33
$ echo $(( ~33 ))
-34
$ echo $(( ~255 ))
-256
$
and my kernel is:
$ uname -a
Linux HOSTNAME 3.2.0-40-generic-pae #64-Ubuntu SMP Mon Mar 25 21:44:41 UTC ...
4
votes
3answers
2k views
how to suppress bash octal number interpretation? (to be interpreted as decimal)
I have this:
date +"%H hours and %M minutes"
I use festival to say it up.. but it says like: "zero nine hours".. I want it to say "nine hours"!
but date always give me 09... so I wonder if bash ...
2
votes
1answer
150 views
Difference between two types of shell arithmetic
What is the difference between the following two shell arithmetic commands:
echo $[ $var1 - 1 ]
echo $(( $var1 - 1 ))
Assuming var1 = 5 for example.
1
vote
2answers
1k views
case + how to implement equal or less or greater in case syntax
My target is to verify a range of number with (only with case + esac), and print the range. So for example:
If the number is between 0 and 80, print >=0<=80
If the number is between 81 and 100 ...
8
votes
5answers
8k views
Binary to hexadecimal and decimal in a shell script
I have a context where I need to convert binary to hexadecimal and decimal and viceversa in a shell script. Can someone suggest me a tool for this?
5
votes
3answers
617 views
bash -e exits when let or expr evaluates to 0
I have a bash script that sets -e so the script will exit on any exit status != 0.
I'm trying to do some basic shell arithmetic assigned to variables and sometimes the expression equals 0 which ...
7
votes
5answers
6k views
How to create a sequence with leading zeroes using brace expansion
When I use the following, I get a result as expected:
$ echo {8..10}
8 9 10
How can I use this brace expansion in an easy way, to get the following output?
$ echo {8..10}
08 09 10
I now that ...
3
votes
2answers
754 views
Error when subtracting two negative numbers in ksh: “assignment requires lvalue”
I am trying to debug someone else's script:
The code line is:
y=$((${oldvalue[$x]}-${newvalue[$x]}))
y gets calculated fine as long as both sides are positive numbers. However, I have a ...
4
votes
1answer
1k views
awk high precision arithmetic
I am looking for a way to tell awk to do high-precision arithmetic in a substitution operation. This involves, reading a field from a file and substituting it with a 1% increment on that value. ...
0
votes
2answers
7k views
How to add arithmetic variables in a script
I want to accumulate the line size of a number of files contained in a folder. I have written the following script:
let a=0
let num=0
for i in folder/*
do
num=`cat $i | wc -l`
...
4
votes
2answers
258 views
Redirect stderr of the double-parentheses construct
I'd like to be able to redirect the stderr of a double-parentheses construct.
For example:
a=$(($var/$var2))
would output some error messages if $var2 = 0, I do not want the user to see this.
I ...
2
votes
4answers
5k views
Calculate variable, and output it to another variable
The only calculator I know is bc. I want to add 1 to a variable, and output to another variable.
I got the nextnum variable from counting string in a file:
nextnum=`grep -o stringtocount ...
4
votes
1answer
402 views
Emacs simple arithmetics in query replace
Is it possible to do the following in emacs:
Query replace all numbers in a region by the number +n, for example if you have:
12 and 7 are nice numbers
let n be 3, then it should transform to
15 ...
4
votes
2answers
242 views
Trying to do arithmetic in Perl rename tool (Debian)
Supposed I have five mp3 files:
01-trackfoo.mp3
02-trackbar.mp3
03-trackbaz.mp3
04-trackabc.mp3
05-trackxyz.mp3
Now I give a quick listen to the files (just mplayer on console will do the trick) ...
4
votes
2answers
4k views
Bash: integer expression expected, using read/test
I'm learning the basics of shell programming, so I wrote something simple like
#!/bin/bash
read var1
read var2
if [ var1 -lt var2 ]; then
echo "var1 is lt var2"
else
echo "var2 is lt var1"
fi
...
2
votes
2answers
1k views
How to divide a list of values by a number in command line?
I am trying to translate a simple program to the command line using unix utilities. For example, if I have a frequency list (after piping through uniq and sort)
5 x
4 y
1 z
I want to print out, ...
6
votes
1answer
658 views
Why does a=0; let a++ return exit code 1?
Try it:
$ a=0
$ let a++
$ echo $?
1 # Did the world just go mad?
$ echo $a
1 # Yes, it did.
$ let a++
$ echo $?
0 # We have normality.
$ echo $a
2
Contrast with this:
$ b=0
$ let b+=1
$ echo $?
0
...
8
votes
7answers
5k views
Doing simple math on the command line using bash functions: $1 divided by $2 (using bc perhaps)
Sometimes I need to divide one number by another. It would be great if I could just define a bash function for this. So far, I am forced to use expressions like
echo 'scale=25;65320/670' | bc
but ...
7
votes
4answers
4k views
creating a sequence of numbers, one per line in a file
Is there a way to create out of thin air, a file that is a sequence of numbers, starting at a given number, one per line?
something like
magic_command start 100 lines 5 > b.txt
and then, b.txt ...
12
votes
6answers
11k views
How to compare to floating point number in a shell script
I want to compare two floating point numbers in a shell script. The following code is not working:
#!/bin/bash
min=12.45
val=10.35
if (( $val < $min )) ; then
min=$val
fi
echo $min
2
votes
4answers
301 views
Generate lists of page numbers for 2-up duplex printing: 2,3,… and 1,4,…
How can I generate the following increments?
2,3,6,7,10,11,14,15,18,19,22,23,26,27,30,31,34,35,38,39,42,43,46,47,...,135
and
...
1
vote
3answers
641 views
Writing a shell script to take output of an executable and perform some calculation
I am not much familiar with shell script. I want to write a shell script for the following pseudo-code:
min=some garbage value
for(i=1 to N){ // N and n will be taken as input for the shell script.
...
3
votes
3answers
9k views
How to calculate values in a shell script?
I run this command in the terminal:
grep "bla bla blah" blah* | echo "Blah: $(wc -l) / $(ls | wc -l) * 100"
And I get this output:
Blah: 44 / 89 * 100
What I expect to see:
49.4
Is there a ...
2
votes
4answers
3k views
Increment number in bash variable string
VERSION="4.0beta12"
NEXT_VERSION=?????
Writing an automatic release script, I have the current version in a variable $VERSION, and I would like to calculate the next version as $NEXT_VERSION.
Rule: ...
3
votes
2answers
371 views
Why does $((40-35)) turn into 5?
What kind of strange shell syntax is hidden behind $((40-35)) and how come it calculates a value?
Example:
$> echo $((40-35))
5
6
votes
2answers
636 views
Using bash “double paren” arithmetic expansion, math fails with leading zero
I have a simple script that deals with hours and minutes.
If I want to calculate number of minutes since midnight having a string s hh:mm I tried splitting string then doing hh * 60 + mm
My problem ...
14
votes
3answers
5k views
Bash: double equals vs -eq
I am doing integer comparison in bash (trying to see if the user is running as root), and I found two different ways of doing it:
Double equals:
if [ $UID == 0 ]
then
fi
-eq
if [ $UID -eq 0 ]
...
2
votes
3answers
3k views
grepping a variable and adding 1 to it
I have a variable containing a leading zeroes number, and I want to grep this variable and that same variable plus one. I made several attempts but ran into errors. Here's what I want to do:
read var
...
-1
votes
1answer
2k views
Sum of grep results
I need to output the sum of a grep results for a certain time, for now i hard coded the time grep but any help will be very much appreciated, my problem is i cant output the results on the script.
If ...
24
votes
9answers
34k views
Is there a way to get the min, max, median, and average of a list of numbers in a single command?
I have a list of numbers in a file, one per line. How can I get the minimum, maximum, median and average values? I want to use the results in a bash script.
Although my immediate situation is for ...
4
votes
2answers
3k views
In bash, how to convert 8 bytes to an unsigned int (64bit LE)?
How can I 'read/interpret' 8 bytes as an unsigned int (Little Endian)?
Perhaps there is a Bash-fu magic conversion for this?
UPDATE:
It seems that something got cross-wired in the interpretation of ...
