CODEWITHSUNDEEP
bashunix
compsciman
compsciman

Reputation: 369

Bash how to ensure a text file is non-empty but adheres to a certain format?

This standard check to see if a file is non-empty can be easily broken:

if [ -s "$FILE" ]; then
    echo "contains stuff"
else
    echo "empty"
fi

Like if I just put a newline in there it will count as something being there. How can I ensure that if something is there it is at least a valid character? I need to ensure the text in a file is in a format like this:

test
test
\n

and not something like this:

\n
\n

Upvotes: 1

Views: 81

Answers (1)

John1024
John1024

Reputation: 113844

Replace

if [ -s "$FILE" ]; then

with

if grep -q . "$FILE"; then

grep . filename returns true (exit code 0) if any line in the file matches . (which, in regex, means any character). Newlines aren't matched. -q tells grep to be quiet so grep -q . filename performs the same test but silently, producing no output.

Upvotes: 3

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