Bash 4+示例。注意:当单词中包含空格时，不使用引号会导致问题。在我看来，总是用Bash引用。

下面是Bash 4+中的一些例子:

例1，在字符串中检查'yes'(不区分大小写):

    if [[ "${str,,}" == *"yes"* ]] ;then

例2，检查字符串中的'yes'(不区分大小写):

    if [[ "$(echo "$str" | tr '[:upper:]' '[:lower:]')" == *"yes"* ]] ;then

例3，检查字符串中的'yes'(区分大小写):

     if [[ "${str}" == *"yes"* ]] ;then

例4，检查字符串中的'yes'(区分大小写):

     if [[ "${str}" =~ "yes" ]] ;then

例5，精确匹配(区分大小写):

     if [[ "${str}" == "yes" ]] ;then

例6，精确匹配(不区分大小写):

     if [[ "${str,,}" == "yes" ]] ;then

例7，精确匹配:

     if [ "$a" = "$b" ] ;then

享受。

你也可以使用用例/esac:

case "$string" in
 "$pattern" ) echo "found";;
esac

或者，如果你不需要else子句:

[ "$x" == "valid" ] && echo "x has the value 'valid'"

a="abc"
b="def"

# Equality Comparison
if [ "$a" == "$b" ]; then
    echo "Strings match"
else
    echo "Strings don't match"
fi

# Lexicographic (greater than, less than) comparison.
if [ "$a" \< "$b" ]; then
    echo "$a is lexicographically smaller then $b"
elif [ "$a" \> "$b" ]; then
    echo "$b is lexicographically smaller than $a"
else
    echo "Strings are equal"
fi

注:

if和[和]之间的空格很重要 >和<是重定向操作符，因此对于字符串分别使用\>和\<转义。

要比较字符串和通配符，使用:

if [[ "$stringA" == *"$stringB"* ]]; then
  # Do something here
else
  # Do something here
fi

我这样做，是兼容Bash和Dash (sh):

testOutput="my test"
pattern="my"

case $testOutput in (*"$pattern"*)
    echo "if there is a match"
    exit 1
    ;;
(*)
   ! echo there is no coincidence!
;;esac