expr

[malladisk]

Hi, I have a file with integers on each line and I want to sum them up.
What's wrong with the following code?

for x in `cat myfile.txt`
do
total=`expr $total + $x`
done
echo $total

I keep getting "expr: Systax error"

Thanks,
SM

 

[vgersh99]

#!/bin/ksh

typeset -i total=0;

for i in $(< myfile.txt) ; do
  total=$(expr ${total} + ${i})
done

echo "total->[${total}]"

vlad
+----------------------------+
| #include<disclaimer.h> |
+----------------------------+

 

[PHV]

If not in ksh like shell:
for x in `cat myfile.txt`
do
total=`expr ${total:=0} + $x`
done
echo $total

In a ksh like shell:
typeset -i total=0 x=0
for x in $(< myfile.txt); do ((total+=x}); done
echo $total

Hope This Helps, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884 or FAQ222-2244

 

[Mike042]

Hi malladisk,

>>> What's wrong with the following code?

The expr command requires $total and $x to exist so that it can add them together. The syntax error is caused because $total doesn't exist on the first time through the for loop. So just put the line:
total=0

before the for loop.

I hope that helps.

Mike

 

[PHV]

Oops, sorry for the typo :~/
In a ksh like shell:
typeset -i total=0 x=0
for x in $(< myfile.txt); do ((total+=x)); done
echo $total

Hope This Helps, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884 or FAQ222-2244

 

[malladisk]

Thanks, guys! I find Vlad's tip extremely useful, that of using typeset so that I don't have to use expr again!
Sashi

 

[olded]

Vlad/PHV:

Could either of you comment on the use of:

for i in `cat filename`

versus:

for i in $(< filename)

The second one really isn't a useless use of cat, UUOC, because it doesn't spawn another shell. Is that correct?

Thanks!


Ed

 

[PHV]

olded, I'm not sure.

The command substitution $(cat file)
can be replaced by the equivalent $(<file). Command substitution
of most special commands that do not perform input/output
redirection is carried out without creating a separate process.

Hope This Helps, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884 or FAQ222-2244