Questions tagged [expr]
expr - evaluate arguments as an expression
26 questions
1
vote
1
answer
43
views
What is expr doing when processing arrays?
I have a BASH script problem that I've narrowed down but I can't understand what I'm seeing. I want to get a substring of an array in a succinct way. Here's what I'm seeing in bash, with 'set -x' so ...
- 920
2
votes
2
answers
99
views
How to add mathematically the results of two commands in Linux
In a Debian Linux shell, I am trying to add the results of two separate commands so that I know the sum of both.
I already tried:
echo $(expr $(du -sh /srv/mysql) + $(du -sh /srv/www))
and ...
- 121
4
votes
1
answer
353
views
Understanding of the regexp match feature of the expr utility
Could anyone help me to understand how the regex match works with the expr utility? I've read its man page and below is an excerpt:
STRING : REGEXP
anchored pattern match of REGEXP in STRING
But I ...
- 1,045
0
votes
1
answer
278
views
Getting syntax error exception for “expr”
I have an xml file which looks like below
INPUT XML FILE
<ReconSummary>
<entryName>Total Deep</entryName>
<Code>777</Code>
<License>L</License>
<Tran>...
3
votes
3
answers
3k
views
Set a variable to the result of a division and subtraction command
I am trying to get the difference of 2 dates in epoch form and convert the number back to days:
EXPIRYEPOCH=$(date --date="$EXPIRYDATE" +%s)
TODAYEPOCH=$(date --date="$TODAYSDATE" +...
- 1,807
5
votes
3
answers
3k
views
Convert only parts of a filename to uppercase
In a shell script program, I need to convert the filenames to uppercase if the converted filename does not already exist. In this particular case I need to change only the basename to uppercase ...
- 193
0
votes
2
answers
591
views
My expr is being printed but not evaluated
The code for the script is:
echo "Years:"
read age
x=`expr $age*365`
echo -e $x
The output when I call this script from the command line is as follows:
Years:
(say I put 20)
20*365
Why is it not ...
0
votes
1
answer
5k
views
'expr: syntax error: unexpected argument' - result from alias [duplicate]
I recently added an alias to my .bash_aliases file:
alias runhole="perfect && cd data_series_test && doa=$(ls -1 | wc -l) && a=$(expr $doa / 2 ) && perfect && ...
8
votes
2
answers
14k
views
How to read string as hex number in bash?
I have the bash line:
expr substr $SUPERBLOCK 64 8
Which is return to me string line:
00080000
I know that this is, actually, a 0x00080000 in little-endian. Is there a way to create integer-variable ...
- 295
1
vote
1
answer
1k
views
awk arithmetic differs from expr
There are some contrast output between awk arithmetic and expr.
Example
expr 11111111111111111111 / 22
gives
505050505050505050
but with awk:
echo '11111111111111111111' | awk '{q=$1/22;;print q}'
...
user305910
1
vote
2
answers
2k
views
Echo calculation to text file [duplicate]
I am working on a project to calculate my overtime at work with a shell script. I have two inputs and want to find if my number is over 800 = 8 hours;
if it is bigger, then it has to print out the ...
- 17
0
votes
1
answer
125
views
Changing a variable value balance
I am practicing unix, self learning so I done some basic coding of creating a cash machine. so far I have done the following and need some guidance on the final hurdle
I am stuck on how I can update ...
- 121
2
votes
1
answer
2k
views
What does this expr do in a shell script?
What does the following do exactly?
newProg=`expr "${newProg}" : ".* -> \(.*\)$"`
if expr "x${newProg}" : 'x/' >/dev/null; then
prog="${newProg}"
else
progdir=`dirname "...
- 10.5k
2
votes
1
answer
967
views
expr and variables
How do I run the script: ./script.sh 1 \* 2
Eventually: ./script.sh 1 '*' 2
How does my script look like:
args="$@" # the first line of the script
result=$(($args))
echo "$args = $result"
Does it ...
- 375
1
vote
2
answers
7k
views
shell - using expr “multiplication table”
I'm learning shell to create a multiplication table, I write code like that:
#!/ in/bash
for i in 1 2 3 4 5 6 7 8 9
do
for j in 1 2 3 4 5 6 7 8 9
do
if [ $j -le $i ]
...
- 13