How to check if a file is empty in Bash?

问题:

I have a file called diff.txt. Want to check if it is empty. Did something like this but couldn't get it working.

if [ -s diff.txt ]
then
        touch empty.txt
        rm full.txt
else
        touch full.txt
        rm emtpy.txt
fi

回答1:

Misspellings are irritating, aren't they? Check your spelling of empty, but then also try this:

#!/bin/bash -e

if [ -s diff.txt ]
then
        rm -f empty.txt
        touch full.txt
else
        rm -f full.txt
        touch empty.txt
fi

I like shell scripting a lot, but one disadvantage of it is that the shell cannot help you when you misspell, whereas a compiler like your C++ compiler can help you.

Notice incidentally that I have swapped the roles of empty.txt and full.txt, as @Matthias suggests.

回答2:

[ -s file.name ] || echo "file is empty"

回答3:

[[ -s file ]] --> Checks if file has size greater than 0

if [[ -s diff.txt ]]; then echo "file has something"; else echo "file is empty"; fi

If needed, this checks all the *.txt files in the current directory; and reports all the empty file:

for file in $(ls *.txt); do if [[ ! -s $file ]]; then echo $file; fi; done

回答4:

While the other answers are correct, using the "-s" option will also show the file is empty even if the file does not exist.
By adding this additional check "-f" to see if the file exists first, we ensure the result is correct.

if [ -f diff.txt ]
then
  if [ -s diff.txt ]
  then
    rm -f empty.txt
    touch full.txt
  else
    rm -f full.txt
    touch empty.txt
  fi
else
  echo "File diff.txt does not exist"
fi

回答5:

@geedoubleya answer is my favorite.

However, I do prefer this

if [[ -f diff.txt && -s diff.txt ]]
then
  rm -f empty.txt
  touch full.txt
elif [[ -f diff.txt && ! -s diff.txt ]]
then
  rm -f full.txt
  touch empty.txt
else
  echo "File diff.txt does not exist"
fi

回答6:

Many of the answers are correct but I feel like they could be more complete / simplistic etc. for example :

# BASH4+ example on Linux :

typeset read_file="/tmp/some-file.txt"
if [ ! -s "${read_file}" ]  || [ ! -f "${read_file}" ] ;then
    echo "Error: file (${read_file}) not found.. "
    exit 7
fi

if $read_file is empty or not there stop the show with exit. More than once I have had misread the top answer here to mean the opposite.