Comparison function that compares two text files in Unix

问题

I was wondering if anyone could tell me if there is a function available in unix, bash that compares all of the lines of the files. If they are different it should output true/false, or -1,0,1. I know these cmp functions exist in other languages. I have been looking around the man pages but have been unsuccessful. If it is not available, could someone help me come up with an alternative solution?

Thanks

回答1:

There are several ways to do this:

cmp -s file1 file2: Look at the value of $?. Zero if both files match or non-zero otherwise.
diff file1 file2 > /dev/null: Some forms of the diff command can take a parameter that tells it not to output anything. However, most don't. After all, you use diff to see the differences between two files. Again, the exit code (you can check the value of $? will be 0 if the files match and non-zero otherwise.

You can use these command in a shell if statement:

if cmp -s file1 file2
then
   echo "The files match"
else
   echo "The files are different"
fi

The diff command is made specifically for text files. The cmp command should work with all binary files too.

回答2:

There is a simple cmp file file command that does just that. It returns 0 if they are equal and 1 if they are different, so it's trivial to use in ifs:

if cmp file1 file1; then
    ...
fi

Hope this helps =)

回答3:

#!/bin/bash

file1=old.txt
file2=new.txt

echo " TEST 1 : "
echo

if [ $( cmp -s ${file1} ${file2}) ]
then
   echo "The files match"
else
   echo "The files are different"
fi

echo
echo " TEST 2 : "
echo
bool=$(cmp -s "$file1" "$file2" )
if cmp -s "$file1" "$file2"
then
   echo "The files match"
else
   echo "The files are different"
fi

echo
echo " TEST 3 : "
echo

md1=$(md5 ${file1});
md2=$(md5 ${file2});

mdd1=$(echo $md1 | awk '{print $4}' ) 
mdd2=$(echo $md2 | awk '{print $4}' ) 
echo $md1
echo $mdd1
echo $md2
echo $mdd2
echo

#if [ $mdd1 = $mdd2 ]; 
if [ $mdd1 -eq $mdd2 ]; 
then
   echo "The files match"
else
   echo "The files are different"
fi

回答4:

You could do an md5 on the two files, then compare the results in bash.

No Unix box here to test, but this should be right.

#!/bin/bash

md1=$(md5 file1);
md2=$(md5 file2);

if [ $md1 -eq $ $md2 ]; then
  echo The same
else
  echo Different
fi

回答5:

echo "read first file" read f1 echo "read second file" read f2

diff -s f1 f2 # prints if both files are identical

来源：https://stackoverflow.com/questions/12736013/comparison-function-that-compares-two-text-files-in-unix

标签

bash

unix

cmp