Bash scripts errors

Question

I'm trying to run those scripts but I keep receiving errors messages:

1-

#!/bin/bash

filename=$1


if [ -f $filename ]
then
    owner=`stat -c %U $filename`
    grep $owner /etc/passwd
    if [ $? -eq 0 ]; then
            perm=`stat -c %a $filename | head -c 1`
            if [ $perm -gt 3 ]; then
                cat $filename | grep NOTE
            fi
        fi
fi

the error message is :

stat: missing operand Try `stat --help' for more information.

2-

#!/bin/bash

NoSum=$1
sum=0
echo "Please enter $NoSum values one at a time"
for (( i=1; i<=$NoSum; i++ ))
do
    echo "Next Value?"
    read num
    let "a = $sum + $num"
    sum=$a
done

echo "The sum is : $sum"

the error message is:

Please enter values one at a time ./scr3: line 6: ((: i<=: syntax error: operand expected (error token is "<=") The sum is : 0

3-

#!/bin/bash

dir=$1

if [ -d $dir ]
    then
    perm=`stat -c %a $dir | head -c 1`
    if [ $perm -gt 5 ]; then
        cd $dir
        for file in $dir/*
        do
            if ! [ -x "$file" ]
            then
                echo "$file"
            fi
        done
    fi
fi

the error message is:

stat: missing operand Try `stat --help' for more information. ./scr4: line 8: [: -gt: unary operator expected

any idea how to fix them ?

Couple of tips (not solving your problem) -- instead of using back-ticks `stat -c %U $filename` use the newer $() notation $(stat -c %U $filename) which eliminates nesting problems -- use braces on your vars $dir --> ${dir} -- consider a = $((sum + num)) vs. let "a = $sum + $num — Stephen P
– Stephen P, Commented Apr 3, 2014 at 1:07
@StephenP Good first suggestion, but don't think there is any benefit to the second one unless you particularly like the syntax or are doing something like "${variable}string" — Reinstate Monica Please
– Reinstate Monica Please, Commented Apr 3, 2014 at 1:15
good suggestions, but to "see" what your problem is, learn to use the shell debug/trace options, set -vx (on), and set +vx (off). This will print the code that is to be executed, and then a 2nd line preceded with + will show the actual command that is run, with values substituted for variable names. While/Until/For loops and nested constructs can be confusing to read at first, focus on the results of the +'d lines. Also adding export PS4='${LINENO} +> will show you the line number of the current script being executed. Good luck. — shellter
– shellter, Commented Apr 3, 2014 at 3:37
@BroSlow @shelter - good points and I use [+|-]vx often. I do use ${var}string enough that, for consistency, I now always use the ${var} form even if a string does not follow. — Stephen P
– Stephen P, Commented Apr 3, 2014 at 18:43

rjv · Accepted Answer · 2014-04-03 00:57:54Z

1

Nothing is wrong about the programs.You are not supplying the command line arguments.You must run it as

1 and 3:

./script.sh <filename>

2:

./script.sh <number>

$1 stands for the first command line argument

answered Apr 3, 2014 at 0:57

rjv

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1 Comment

Reinstate Monica Please Over a year ago

@user3357669 You should accept this as the answer if it fixed the issue, though I would still change the scripts if you have permission to, as they will fail in quite a large number of cases.

Reinstate Monica Please · Accepted Answer · 2014-04-03 00:52:05Z

0

You need to quote variables in bash to prevent word-splitting issues, both in test brackets [] and most of the time in other use.

So your first script would be

#!/bin/bash

filename="$1"


if [ -f "$filename" ]
then
    owner="`stat -c %U "$filename"`"
    grep "$owner" /etc/passwd
    if [ $? -eq 0 ]; then
            perm="`stat -c %a "$filename" | head -c 1`"
            if [ "$perm" -gt 3 ]; then
                cat "$filename" | grep NOTE
            fi
    fi
fi

The others have similar erros

answered Apr 3, 2014 at 0:52

Reinstate Monica Please

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