Linux Shell Basics (vii)

Vii. Process Control   conditional judgment control in bash Scripts   [] (the expression in [] is true)  && (the result of the front is true when executing the command behind)   | | (The result of the front is false when executing the command behind)  -if -case  loop control  -while -utile -for -break - continue#[ABC] #echo $?0 (for true) #[] #echo $?1 (for false) #["$USER" = "BYF" [The Meaning of ' $?* ' is to remove the special meaning of the character, "" The double quotation marks only remove the special meaning of the space) #echo $? 1#[$USER = root] #echo $?0#[$USER = root] && echo Hello Roothello root#[-x/etc/] && echo Hellohello#man Bash input/-w to find, n Find Next #-r (Read)-W (write)----------------------------------(link)-B (Block's adapter file)-c#[-b/dev/hda]&& echo You ha ve a IDE DEVICE#[-B/DEV/SDA]&& echo you have a SCSI deviceyou has a SCSI device#[-f/usr/sbin/httpd] && echo Please install httpt againplease install httpd again#vi b#!/bin/bashread aaaif [$AAA = byf]thenecho Hello byfelif [$AAA = root] thenecho Hello rootelse  echo ' get out of Here ' fiwq#./b#bash-v./b (see Execute to that command) #bash-VX./b (view error command line, For debugging, you can see the value of each variable) c and bash debug the difference c is a pure binary file, debugging requires the corresponding development environment settings Breakpoint Bash isText files that can be directly detected where the error is ##! /bin/bashread Aaacase $ (Take out the value of the variable) AAA inBYF)echo Hello ByfEcho Nice to meet;;( Indicates end)Root)echo Hello Rootecho I miss much;;* )Echo Get out Here;; Esac:wq#bash./cbyf-eq = Same-ne! = Different-gt >-lt <-ge >=-le <=-z is empty #!/bin/bashaaa= "' pgrep httpd '" [-Z "$AAA" ("3186 3188 3189 3190 3191 3192 3193 319 4 3195 "Remove the space in the variable)]&& echo httpd ' httpd is not running! ' && exitfor i in $AAADoKill-9 $iDoneecho httpd is killedwq#chmod a+x d#./d#./d#!/bin/bashfor AAA in 111 222 333/etc/profile.d/*.hdoEcho $aaa (chmod a + x $aaa batch operation) Done#chmod a+x e#./e111222333/etc/profile.d/colorls.sh/etc/profile.d/glib2.sh/etc/ profile.d/gnome-ssh-askpass.sh/etc/profile.d/kde.sh/etc/profile.d/lang.sh/etc/profile.d/less.sh/etc/profile.d/ qcd.sh/etc/profile.d/qt.sh/etc/profile.d/udisks-bash-completion.sh/etc/profile.d/vim.sh/etc/profile.d/ Which2.sh#seq 1 10012 ... 100#!/bin/bashfor aaa in ' seq 1 ' doEcho $aaa; Sleep 1 (Semicolon does not add carriage return, no semicolon added line)(Echo-n "$AAA"Sleep 1) done##!/bin/bashiii=0while [$III-lt 100]Doi=$[$IIII +1]Echo-n "$III"Done##!/bin/bashiii=0until [$III-GT 100]Doiii=$[$III +1]Echo-n "$III"Doneunset Iii:wq##!/bin/bashwhiletrue DoRead AAAIf ["$AAA" = "ddd"]ThenBreakFidone

Linux Shell Basics (vii)