shell指令碼：test命令 if-then for while 學習筆記

test 檔案運算子：

-b file  如果檔案為一個塊特殊檔案，則為真

-c file  如果檔案為一個字元特殊檔案，則為真

-d file  如果檔案為一個目錄，則為真

-e file  如果檔案存在，則為真

-f file  如果檔案為一個普通檔案，則為真

-g file  如果設定了檔案的 SGID 位，則為真

-G file  如果檔案存在且歸該組所有，則為真

-k file  如果設定了檔案的粘著位，則為真

-O file  如果檔案存在並且歸該使用者所有，則為真

-p file  如果檔案為一個具名管道，則為真

-r file  如果檔案可讀，則為真

-s file  如果檔案的長度不為零，則為真

-S file  如果檔案為一個通訊端特殊檔案，則為真

-t fd   如果 fd 是一個與終端相連的開啟的檔案描述符（fd 預設為 1），則為真

-u file  如果設定了檔案的 SUID 位，則為真

-w file  如果檔案可寫，則為真

-x file  如果檔案可執行，則為真

if-then結構化命令 執行個體：

file=test1touch fileif [ -s file ]then        echo " The file file exits and has data in it"else        echo " The file file exits ,but  has not  data in it"fidate > fileif [ -s file ]then        echo "the file file has data in it"else        echo "the file file is also empty ,no data hummm"fiif [ 1.c -nt one2.c ]then        echo "1.c is newer than one2.c"else        echo "1.c is not newer than one2.c"fi

for命令：

for var in list
do
   commands
done 

執行個體：

list="one one2 one4 one5"list=$list" one6"//在已經存在的變數中添加新的資料for state in $listdo        echo "state is $state"done結果：./forteststate is onestate is one2state is one4state is one5state is one6

讀取命令中的值：file="states"for state in 'cat $file'do        echo "visit word $state"done~      

while命令

格式：

while the command
do
    other commands
done

執行個體：

var1=10 #賦值是不能有空格的 有空格就會出現問題 例如: /last: 第 3 行: [: -gt: 期待一元運算式等echo "var1 is $var1"while [ $var1 -gt 0 ]do        echo "the var1 is $var1"        var1=$[$var1 -1 ]done

結果：

the var1 is 10the var1 is 9the var1 is 8the var1 is 7the var1 is 6the var1 is 5the var1 is 4the var1 is 3the var1 is 2the var1 is 1