变量赋值问题，大家看看

junglegq

两个程序，变量name的输出结果不同，大家给诊断一下
#!/bin/bash
declare -i a=1
declare name=""
while [ $a -le 5 ]; do
        echo $a
        a=a+1
        name="neil"
done
echo $name
echo $a

name输出是： neil

#!/bin/bash
declare -i a=1
declare name=""
cat /tmp/db | while read line; do
        echo $a
        a=a+1
        name="neil"
done
echo $name
echo $a
其中，/tmp/db只有两行，
name输出为空

Edengundam

环境变量 + sub shell

寂寞烈火

while read line;do
....
done<filename

lgfang

comp.unix.shell 的 FAQ

33. Why do I lose the value of global variables that are set in a loop.

    Given the following program

      #!/bin/sh
      x="this is the initial value of x"
      cat dataFile | while read line;do
        x="$line"
      done
      echo x = $x

     You may get the following for output

       x = this is the initial value of x

     This is because in the Bourne shell redirected control structures
     run in a subshell, so the value of x only gets changed in the
     subshell, and is lost when the loop ends.

     In other shells the same result may be seen because of the way
     pipelines are handled. In shells other than ksh (not pdksh) and
     zsh elements of a pipeline are run in subshells. In ksh and zsh,
     the last element of the pipeline is run in the current shell.

     An alternative for non-Bourne shells is to use redirection
     instead of the pipeline

      #!/bin/sh
      x="this is the initial value of x"
      while read line;do
        x="$line"
      done < dataFile
      echo x = $x

    With a Bourne shell you need to reassign file descriptors, so no
    pipline or redirection in the loop is involved.

      exec 3<&0         # save stdin
      exec < file
      while read line; do
        x=$line
      done
      exec 0<&3        # restore stdin

    Note that putting #!/bin/sh at the top of a script doesn't
    guarantee you're using the Bourne shell. Some systems link /bin/sh
    to some other shell. Check your system documentation to find out
    what shell you're really getting in this case.

junglegq

谢谢lgfang啦，说的够详细