shell编程---if语句

                                                if语句

1、if..then..else...fi

  1 #! /bin/bash
  2 echo $PWD
  3 #if judagement condition expression
  4 if grep "shell" ./1.txt  >/dev/null
  5 #if grep "Shell" ./1.txt  >/dev/null
  6 then
  7         echo "the string exists in in current path"
  8 else
  9         echo "the string dosen't exist in current path"
 10 fi

andy@andy-virtual-machine:~/test_shell$ cat 1.txt 
shell
andy@andy-virtual-machine:~/test_shell$ 

2、if...then...fi

  1 #! /bin/bash
  2 echo $PWD
  3 #if judagement condition expression
  4 if grep "shell" ./1.txt  >/dev/null
  5 #if grep "Shell" ./1.txt  >/dev/null
  6 then
  7         echo "the string exists in in current path"
  8 #else
  9 #       echo "the string dosen't exist in current path"
 10 fi

andy@andy-virtual-machine:~/test_shell$ cat 1.txt 
shell
andy@andy-virtual-machine:~/test_shell$