Case insensitive comparison of strings in shell sc

问题:

The == operator is used to compare two strings in shell script. However, I want to compare two strings ignoring case, how can it be done? Is there any standard command for this?

回答1:

if you have bash

str1="MATCH"
str2="match"
shopt -s nocasematch
case "$str1" in
 $str2 ) echo "match";;
 *) echo "no match";;
esac

otherwise, you should tell us what shell you are using.

alternative, using awk

str1="MATCH"
str2="match"
awk -vs1="$str1" -vs2="$str2" 'BEGIN {
  if ( tolower(s1) == tolower(s2) ){
    print "match"
  }
}'

回答2:

In Bash, you can use parameter expansion to modify a string to all lower-/upper-case:

var1=TesT
var2=tEst

echo ${var1,,} ${var2,,}
echo ${var1^^} ${var2^^}

回答3:

All of these answers ignore the easiest and quickest way to do this (as long as you have Bash 4):

if [ "${var1,,}" = "${var2,,}" ]; then
  echo ":)"
fi

All you're doing there is converting both strings to lowercase and comparing the results.

回答4:

Same as answer from ghostdog74 but slightly different code

shopt -s nocasematch
[[ "foo" == "Foo" ]] && echo "match" || echo "notmatch"
shopt -u nocasematch

回答5:

One way would be to convert both strings to upper or lower:

test $(echo "string" | /bin/tr '[:upper:]' '[:lower:]') = $(echo "String" | /bin/tr '[:upper:]' '[:lower:]') && echo same || echo different

Another way would be to use grep:

echo "string" | grep -qi '^String$' && echo same || echo different

回答6:

For korn shell, I use typeset built-in command (-l for lower-case and -u for upper-case).

var=True
typeset -l var
if [[ $var == "true" ]]; then
    print "match"
fi

回答7:

Very easy if you fgrep to do a case-insensitive line compare:

str1="MATCH"
str2="match"

if [[ $(fgrep -ix $str1 <<< $str2) ]]; then
    echo "case-insensitive match";
fi

回答8:

Here is my solution using tr:

var1=match
var2=MATCH
var1=`echo $var1 | tr '[A-Z]' '[a-z]'`
var2=`echo $var2 | tr '[A-Z]' '[a-z]'`
if [ "$var1" = "$var2" ] ; then
  echo "MATCH"
fi

回答9:

grep has a -i flag which means case insensitive so ask it to tell you if var2 is in var1.

var1=match 
var2=MATCH 
if echo $var1 | grep -i "^${var2}$" > /dev/null ; then
    echo "MATCH"
fi

回答10:

shopt -s nocaseglob

回答11:

For zsh the syntax is slightly different:

> str1='MATCH'
> str2='match'
> [ "$str1" == "$str2:u" ] && echo 'Match!'
Match!
>

This will convert str2 to uppercase before the comparison.

More examples for changing case below:

> xx=Test
> echo $xx:u
TEST
> echo $xx:l
test

回答12:

I came across this great blog/tutorial/whatever about dealing with case sensitive pattern. The following three methods are explained in details with examples:

1. Convert pattern to lowercase using tr command

opt=$( tr '[:upper:]' '[:lower:]' <<<"$1" )
case $opt in
        sql)
                echo "Running mysql backup using mysqldump tool..."
                ;;
        sync)
                echo "Running backup using rsync tool..."
                ;;
        tar)
                echo "Running tape backup using tar tool..."
                ;;
        *)
                echo "Other options"
                ;;
esac

2. Use regex with case patterns

opt=$1
case $opt in
        [Ss][Qq][Ll])
                echo "Running mysql backup using mysqldump tool..."
                ;;
        [Ss][Yy][Nn][Cc])
                echo "Running backup using rsync tool..."
                ;;
        [Tt][Aa][Rr])
                echo "Running tape backup using tar tool..."
                ;;
        *)
                echo "Other option"
                ;;
esac

3. Turn on nocasematch

opt=$1
shopt -s nocasematch
case $opt in
        sql)
                echo "Running mysql backup using mysqldump tool..."
                ;;
        sync)
                echo "Running backup using rsync tool..."
                ;;
        tar)
                echo "Running tape backup using tar tool..."
                ;;
        *)
                echo "Other option"
                ;;
esac

shopt -u nocasematch