Shell script: convert string to number

[svk]

Hello,

I'm very new to shell scripting in Bash.

I'm trying to figure out how to treat the output of stat -c %s filename as a number, and not as a string. If you run that command, it will output the size of the file in bytes.

Here's the script I'm working on. It iterates over every file in the working directory, and attempts to print the cumulative size of all the files over which it iterated so far.



#!/bin/bash
# print-cumulative-sizes.sh

declare SIZE=0
declare TOTAL=0

for file in *; do {
SIZE=`stat -c %s $file`;
TOTAL=`expr $SIZE+$TOTAL`;
echo $TOTAL;
}; done


The problem should be evident from the output:

serg@bijou:~/Pictures$ ./print-cumulative-sizes.sh
1036228+0
970325+1036228+0
1108950+970325+1036228+0
1476318+1108950+970325+1036228+0
1027836+1476318+1108950+970325+1036228+0
1050479+1027836+1476318+1108950+970325+1036228+0
1156703+1050479+1027836+1476318+1108950+970325+103 6228+0
1215533+1156703+1050479+1027836+1476318+1108950+97 0325+1036228+0
960132+1215533+1156703+1050479+1027836+1476318+110 8950+970325+1036228+0
1569659+960132+1215533+1156703+1050479+1027836+147 6318+1108950+970325+1036228+0
1149074+1569659+960132+1215533+1156703+1050479+102 7836+1476318+1108950+970325+1036228+0
4096+1149074+1569659+960132+1215533+1156703+105047 9+1027836+1476318+1108950+970325+1036228+0
98528+4096+1149074+1569659+960132+1215533+1156703+ 1050479+1027836+1476318+1108950+970325+1036228+0
142+98528+4096+1149074+1569659+960132+1215533+1156 703+1050479+1027836+1476318+1108950+970325+1036228 +0
142+142+98528+4096+1149074+1569659+960132+1215533+ 1156703+1050479+1027836+1476318+1108950+970325+103 6228+0

See what's wrong? How can I get bash to treat my $SIZE and $TOTAL variables as numbers, not as strings?

Thank you in advance for any help!

[ghostdog74]

stat can take in shell wildcards. so there's no need for a loop


stat -c %s * | awk '{s=s+$0}END{print "size: "s" bytes"}'


else, you can use bc instead of expr


echo "1+2" | bc

[WW]

ghostdog74's awk solution is short and sweet, but if you want to stick with your bash code, use let for the arithmetic:


#!/bin/bash
# print-cumulative-sizes.sh

declare SIZE=0
declare TOTAL=0

for file in *; do
SIZE=`stat -c %s $file`;
let TOTAL+=SIZE;
echo $TOTAL;
done


EDIT: I've been using C++ lately, so I didn't even notice those curly braces around the statements in the for loop. BASH doesn't use braces like that.

EDIT 2: This variation uses a single call to stat:


#!/bin/bash
# print-cumulative-sizes.sh

declare TOTAL=0

SIZES=`stat -c %s *`
for SIZE in ${SIZES}; do
let TOTAL+=SIZE
echo $TOTAL
done
echo "TOTAL=$TOTAL"

[geirha]

Your initial script should work if you just add some spaces around the + for the expr-command


$ expr 2+2
2+2
$ expr 2 + 2
4


You can also use bash's (( )) and $(( )) for integer arithmetics

$ TOTAL=0; SIZE=10
$ echo $TOTAL
0
$ ((TOTAL+=SIZE))
$ echo $TOTAL
10
$ echo $((TOTAL+=SIZE))
20