syntax error operand expected (error token is "-") in shell script

Question

Inside the script there is one error i am getting as syntax error operand expected (error token is "-") at line 109

#!/bin/ksh
..............
while read file
do 
    upd_time=$((`date +%s`-`stat -c %Y ${file}`))     #At this line getting error
    file_nm=`basename "${file}"`
..................

In the above live getting error as syntax error operand expected (error token is "-").

You'll get a possibly clearer error message if you correctly quote the expansion of $file. Also, you should use $(...), not backticks, for command substitutions. — chepner
– chepner, Commented Dec 22, 2022 at 14:28

chepner · Accepted Answer · 2022-12-22 14:31:51Z

1

You are trying to call stat when file doesn't have a value:

$ unset file
$ stat -c %Y $file
stat: missing operand
Try 'stat --help' for more information.

If you correctly quote $file, you'll get a slightly better error message:

$ stat -c %Y "$file"
stat: cannot stat '': No such file or directory

If you aren't positive about the contents of your input file, try verifying that $file actually contains an existing file before calling stat:

while IFS= read -r file
do 
    [ -e "$file" ] || continue

    upd_time=$(( $(date +%s) - $(stat -c %Y "$file") ))
    file_nm=$(basename "$file")
    ...
done

answered Dec 22, 2022 at 14:31

chepner

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4 Comments

Mr. Over a year ago

Thanks @chepner one of the file was missing

Mr. Over a year ago

but @chepner in script echo $file & file both were missing so root cause would be both or just only file missing. I just want to confirm

chepner Over a year ago

Both would be separate errors resulting from attempting to use an empty string where a non-empty string was expected. That's why I check once, not just to see if file is non-empty, but to see if it actually refers to a file that you can stat. (basename will work on a path whether the name exists or not, but supposedly future uses of file_nm would require the file to exist.)

Mr. Over a year ago

any idea on below question stackoverflow.com/questions/75007309/…

Jack · Accepted Answer · 2022-12-22 13:12:35Z

0

I have reproduced your error:

tmp.txt:

/bin/sh

/bin/bash

test.sh:

while read file; do
  upd_time=$((`date +%s`-`stat -c %Y ${file}`))
  echo $upd_time
done < tmp.txt

output:

44421445
stat: missing operand
Try 'stat --help' for more information.
-bash: 1671714632-: syntax error: operand expected (error token is "-")

You have a blank line in your input file.

answered Dec 22, 2022 at 13:12

Jack

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5 Comments

Mr. Over a year ago

Thanks for your reply, means if i remove extra blank line then my issue get resolved ?? Actually in main script file there is no any extra blank line but i haven't use echo $upd_time in shell script.

Jack Over a year ago

Not your script file, but the input file to the loop.

chepner Over a year ago

I.e., $file is expanding to an empty string.

Mr. Over a year ago

@chepner $file is a csv file which is in another file directory.

chepner Over a year ago

You may be expecting it to be the name of a CSV file, but it's not.

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