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This article introduces the relevant knowledge of "what are the IF judgment conditions under linux". In the operation process of actual cases, many people will encounter such difficulties. Next, let Xiaobian lead you to learn how to deal with these situations! I hope you can read carefully and learn something!

UNIX shell comparison characters written:

-eq equals-ne does not equal-gt greater than-lt less than-le less than or equal to-ge greater than or equal to-z

Empty string = two characters equal!= Two characters unequal-n non-empty string

No matter what programming language, conditional judgment is indispensable. Shell is no exception.

if list thendo something hereif list thendo another thing heresedo something else herefi

An example:

#!/ bin/shSYSTEM=`uname -s` #Get the operating system type, my local is linuxif [ $SYSTEM = "Linux" ] ; then #If linux output linux string echo "Linux"elif [ $SYSTEM = "FreeBSD" ] ; thenecho "FreeBSD"elif [ $SYSTEM = "Solaris" ] ; thenecho "Solaris"elseecho "What? "fi #judgment ends with fi

It's basically the same as any other scripting language. Not much difference. However, it is worth noting that. […] the judgment within. The description reads as follows:

1 string judgment

str1 = str2

True if two strings have the same content and length str1 != str2

true if str1 and str2 are unequal-n str1

True if string length is greater than 0 (string is not empty) -z str1

True when string length is 0 (empty string) str1

True when string str1 is non-empty

2 Number of Judgments

int1 -eq int2 is true

int1 -ne int2 is true

int1 -gt int2 int1 is greater than int2 is true

int1 -ge int2 int1 is greater than or equal to int2 is true

int1 -lt int2 int1 less than int2 is true

int1 le int2 int1 less than or equal to int2 is true

3 If conditional statements related to files

-r file User readable is true

-w file user can write true

-x file user executable is true

-f file file is true for regular files

-d file is true for directory

-c file file is character special file is true

-b file file is block special file is true

-s file True if file size is non-zero

-t file True when the device specified by the file descriptor (default 1) is terminal

4 Complicated logic judgments

-a and-o or! non

The syntax is simple, but when used in SHELL, it can implement powerful functionality or execute logic.

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