Error "expr: command not found" in bourne script

Question

I am building a bourne script for a class, and am encountering an issue with this loop. Basically I am building a loop to go through all the files in a specified directory and determine how many files and directories there are as well as how many files are readable, writeable, and/or executable. The issue is, when I run the script it returns the following errors:

assignment4.sh: line 61: expr: command not found
assignment4.sh: line 61: expr: command not found
assignment4.sh: line 36: expr: command not found
assignment4.sh: line 41: expr: command not found
assignment4.sh: line 48: expr: command not found
assignment4.sh: line 55: expr: command not found
assignment4.sh: line 36: expr: command not found
assignment4.sh: line 41: expr: command not found
assignment4.sh: line 48: expr: command not found
assignment4.sh: line 36: expr: command not found
assignment4.sh: line 41: expr: command not found
assignment4.sh: line 48: expr: command not found

the section of code causing this error is as follows:

for filename in "$PATH"/"$1"/*
do
    if [ -f "$filename" ]
    then
        files=`expr $files + 1`

        if [ -r "$filename" ]
        then 
        readable=`expr $readable + 1`
        fi

        if [ -w "$filename" ]
        then    
            writeable=`expr $writeable + 1`
        fi

        if [ -x "$filename" ]
        then 
            executable=`expr $executable + 1`
        fi
    elif [ -d "$filename" ] 
    then
        directories=`expr $directories + 1`
    fi
done

I know that expr is on the machine I'm running because I used it earlier and it was working, though I did have to change the format of my statement utilizing it as before they were formatted

var=`expr $var+1`

and were not updating the variable's value the correct way.

Have you changed your $PATH? What does type -a expr print? — Keith Thompson
– Keith Thompson, Commented Dec 4, 2014 at 1:14
Bourne, or POSIX sh? Moderately-old Solaris is the only remotely modern operating system where /bin/sh is still pre-POSIX Bourne; dash, ash, busybox sh, etc. are POSIX sh compliant (a standard itself derived in large part from ksh), not Bourne. — Charles Duffy
– Charles Duffy, Commented Dec 4, 2014 at 1:19
From the code it looks like you chose PATH as a variable name, and accidentally overrode the shell search path. — that other guy
– that other guy, Commented Dec 4, 2014 at 1:25
This is why local, non-exported variables should be lower-case -- so you don't override an environment variable or a builtin by mistake. — Charles Duffy
– Charles Duffy, Commented Dec 4, 2014 at 1:28
For readability: test -r "$filename" && : $((readable += 1)) — William Pursell
– William Pursell, Commented Dec 4, 2014 at 12:54

Andras · Accepted Answer · 2014-12-04 01:19:09Z

2

what's the $PATH of the script when it runs? expr is always present (traditionally in /bin, but in /usr/bin on linux)

but you can't iterate on $PATH/$1/*, because PATH is like /bin:/usr/bin:/usr/local/bin which does not match any directory. I think you want for filename in $(echo -n $PATH | tr : ' ')/$1/* or some such

answered Dec 4, 2014 at 1:19

Andras

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3 Comments

neomang Over a year ago

I did actually change the $PATH value, because it wasn't taking my to my CWD. I think instead I'll use for filename in `pwd`/$1/* simply because I'm not sure what the tr : ' ' section of your suggested code does, my course isn't particularly in-depth.

Charles Duffy Over a year ago

@Neomang, use "$PWD/$1/"* instead. If you don't quote the $1, it'll get string-split, so any filename with spaces in $1 won't behave correctly.

chepner Over a year ago

Your problem was that you overwrote the value of PATH, which is what the shell uses to find executables like expr. Don't use PATH (or any other all-caps variable names, for that matter) for your own purposes.

Charles Duffy · Accepted Answer · 2014-12-04 01:20:33Z

0

If this is not Bourne but POSIX sh (that is, a shell compatible with behavior standardized in the early 90s rather than one direct from the 70s), you can use:

readable=$((readable + 1))

...rather than relying on expr.

answered Dec 4, 2014 at 1:20

Charles Duffy

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