Bash字符串处理（与Java对照） - 16.判断是否以另外的字符串开头

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Bash字符串处理（与Java对照） - 16.判断是否以另外的字符串开头

In Java

String.startsWith

boolean startsWith(String prefix)
测试此字符串是否以指定的前缀开始。

boolean startsWith(String prefix, int toffset)
测试此字符串是否以指定前缀开始，该前缀以指定索引开始。相当于 this.substring(toffset).startsWith(prefix)

StringUtils.startsWith & StringUtils.startsWithIgnoreCase & StringUtils.startsWithAny

org.apache.commons.lang.StringUtils startsWith方法写道

public static boolean startsWith(String str, String prefix)

Check if a String starts with a specified prefix.

nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case sensitive.

StringUtils.startsWith(null, null) = true
StringUtils.startsWith(null, "abc") = false
StringUtils.startsWith("abcdef", null) = false
StringUtils.startsWith("abcdef", "abc") = true
StringUtils.startsWith("ABCDEF", "abc") = false

Parameters:
str - the String to check, may be null
prefix - the prefix to find, may be null
Returns:
true if the String starts with the prefix, case sensitive, or both null

org.apache.commons.lang.StringUtils startsWithIgnoreCase方法写道

public static boolean startsWithIgnoreCase(String str, String prefix)

Case insensitive check if a String starts with a specified prefix.

nulls are handled without exceptions. Two null references are considered to be equal. The comparison is case insensitive.

StringUtils.startsWithIgnoreCase(null, null) = true
StringUtils.startsWithIgnoreCase(null, "abc") = false
StringUtils.startsWithIgnoreCase("abcdef", null) = false
StringUtils.startsWithIgnoreCase("abcdef", "abc") = true
StringUtils.startsWithIgnoreCase("ABCDEF", "abc") = true

Parameters:
str - the String to check, may be null
prefix - the prefix to find, may be null
Returns:
true if the String starts with the prefix, case insensitive, or both null

org.apache.commons.lang.StringUtils startsWithAny方法写道

public static boolean startsWithAny(String string, String[] searchStrings)

Check if a String starts with any of an array of specified strings.

StringUtils.startsWithAny(null, null) = false
StringUtils.startsWithAny(null, new String[] {"abc"}) = false
StringUtils.startsWithAny("abcxyz", null) = false
StringUtils.startsWithAny("abcxyz", new String[] {""}) = false
StringUtils.startsWithAny("abcxyz", new String[] {"abc"}) = true
StringUtils.startsWithAny("abcxyz", new String[] {null, "xyz", "abc"}) = true

Parameters:
string - the String to check, may be null
searchStrings - the Strings to find, may be null or empty
Returns:
true if the String starts with any of the the prefixes, case insensitive, or both null

In Bash

使用[[ ]] 模式匹配来判断是否以别的字符串开头（推荐方式）

格式：[[ $STR == $PREFIX* ]]

[root@web ~]# STR=ISO9001
[root@web ~]# PREFIX=ISO
[root@web ~]# [[ $STR == $PREFIX* ]] && echo "starts"
starts
[root@web ~]# PREFIX="ISO 9"
[root@web ~]# [[ $STR == $PREFIX* ]] && echo "starts"
[root@web ~]# STR="Yes ISO9001"
[root@web ~]# PREFIX=ISO
[root@web ~]# [[ $STR == $PREFIX* ]] && echo "starts"
[root@web ~]#

使用[[ ]] 正则表达式匹配来判断是否以别的字符串开头

格式：[[ $STR =~ ^$PREFIX ]]

注意：必须加上^，否则所有包含该字符串的也会匹配，而不只是以该字符串开头的。

[root@web ~]# PREFIX=ISO
[root@web ~]# STR=ISO9001
[root@web ~]# [[ $STR =~ ^$PREFIX ]] && echo "starts"
starts
[root@web ~]# STR="Yes ISO9001"
[root@web ~]# [[ $STR =~ ^$PREFIX ]] && echo "starts"
[root@web ~]#

以截取子串判断相等的方式来判断是否以别的字符串开头

格式：N=${#PREFIX}; [ "${STR:0:N}" == "$PREFIX" ]

[root@web ~]# PREFIX=ISO
[root@web ~]# STR=ISO9001
[root@web ~]# [ "${STR:0:3}" == "$PREFIX" ] && echo "starts"
starts
[root@web ~]# N=${#PREFIX}
[root@web ~]# [ "${STR:0:N}" == "$PREFIX" ] && echo "starts"
starts
[root@web ~]# [ "${STR:0:$N}" == "$PREFIX" ] && echo "starts"
starts
[root@web ~]#

用case语句来判断是否以别的字符串开头

正确：case "$STR" in "$PREFIX"*) echo "starts"; esac

错误：case "$STR" in "$PREFIX*") echo "starts"; esac

注意*不能写在双引号里面，否则不灵。

[root@web ~]# PREFIX=ISO
[root@web ~]# STR=ISO9001
[root@web ~]# case "$STR" in "$PREFIX*") echo "starts"; esac
[root@web ~]# case "$STR" in "$PREFIX"*) echo "starts"; esac
starts
[root@web ~]#