The judgment statement in the Linux shell

Remember that if and the [] are whitespace

1. String judgment

STR1 = str2 When two strings have the same content, length is true
Str1! = str2 True when string str1 and str2 are not equal
-N str1 True when the length of the string is greater than 0 (string non-null)
-Z str1 True when the string length is 0 (empty string)
STR1 is True when string str1 is not empty

2, the number of the judgment

Int1-eq int2 Two numbers equal to True
Int1-ne Int2 Two number is true
INT1-GT Int2 int1 greater than Int2 is true
Int1-ge Int2 int1 greater than or equal to Int2 true
Int1-lt Int2 int1 Less than Int2 is true
Int1-le Int2 int1 less than or equal to Int2 true

3 Judgment of the document

-r file user readable as True
-W file user can write as true
-X file user can execute as true
-F file is true for regular files
-d file files are directory-True
-C File file is true for character special files
-B file files are true for block special files
-S file files non-0 o'clock True
-T file is true when the specified device is terminal (default = 1)

3. Complex logic judgment

-A and
-O or
! Non -

Here are some examples of usages:

#!/bin/sh
Mypath= "/var/log/httpd/"
Myfile= "/var/log/httpd/access.log"

#这里的-x parameter determines whether $mypath exists and has executable permissions
if [!-X "$myPath"]; Then
mkdir "$myPath"
Fi

#这里的-D parameter to determine if $mypath exists
if [!-D "$myPath"]; Then
mkdir "$myPath"
Fi

#这里的-F parameter to determine if $myfile exists
if [!-F "$myFile"]; Then
Touch "$myFile"
Fi

#其他参数还有-n,-n is to determine whether a variable has a value
if [!-n "$myVar"]; Then
echo "$myVar is empty"
Exit 0
Fi

#两个变量判断是否相等
If ["$var 1" = = "$var 2"]; Then
Echo ' $var 1 eq $var 2 '
Else
Echo ' $var 1 not EQ $var 2 '
Fi

If List Then
Do something here
Elif List Then
Do another thing here
Else
Do something else here
Fi

EX1:

#!/bin/sh

System= ' uname-s ' #获取操作系统类型, I'm local Linux

if [$SYSTEM = "Linux"]; Then #如果是linux的话打印linux字符串
echo "Linux"
elif [$SYSTEM = "FreeBSD"]; Then
echo "FreeBSD"
elif [$SYSTEM = "Solaris"]; Then
echo "Solaris"
Else
echo "What?"
Fi #ifend

Basically the same as other scripting languages. There's no big difference. But it's worth noting that. [] inside the condition to judge.

=========================================================================

#. $HOME/.bash_profile
CD $HOME
Sh. bash_profile
CD $HOME/jnjzapp/sos_dx/
Echo-e ' Start '
./jn_card_dx.sh
Wait
#sqlplus $DBSTR <<start_a
# @jn_card_dx. sql
#/
#commit;
#exit;
#START_A
CD $HOME/jnjzapp/sos_dx/data/
if [!-D bqmsg]; Then
mkdir bqmsg
Fi
#mkdir bqmsg
CD $HOME/jnjzapp/sos_dx/
Sqlplus $DBSTR <<start
@sos. sql;
Commit
Exit
START
Objdir= ' date-d ' Days ' +%y%m%d '
Echo $objdir
#cp jn_card_sos.txt $objdir. txt

The judgment statement in the Linux shell