第04章 shell程序设计.ppt

* * * ? 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary. * 左“{“后面应有一个空格，右括号”｝“之前有一个； 在圆括号内的命令不会改变父shell变量值 * * * * ? 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary. * 以字母或下划线打头的字母、数字和下划线符号的序列 * ? 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary. * Read 变量 n 从给定文件描述字的文件中读取数据，其中n为文件描述字。例如，read name 3 * * ? 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary. * 环境变量是shell本身定义的变量，这组变量由shell本身维护和使用，它们往往与用户运行的环境有关。 IFS 也成为定界符。在默认的情况下，IFS的值为空白符（空格、制表符和回车符）。例如，在命令行中命令名、选择项和各参数之间通常都用空格分开 * ? 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary. * Export命令用于显示本进程利用export命令转出的全部变量，env或printenv列出所有被转出的变量，包括本进程及以前的“祖先进程”所转出的变量 * * * ? 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary. * 文件名前的圆点（.）和路径名中的（/）必须显示匹配 * ? 在[]内失去通配能力，只作为字符来使用 * * * * * * * ? 2004 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary. * * * * * * * * * * * * * * * * exit命令 exit [ n ] 算术表达式 +, -, \*, /, % expr n1 运算符 n2 expr 12 \* 12 函数 函数名( ) { 命令表 } $cat ex13 abc() { echo “Begin” echo $a $b $ c echo $1 $2 $3 echo “End” } a=5 b=10 c=99 abc First Second Third $ex13 Begin 5 10 99 First Second Third End 循环体中其他命令 1. break命令 格式为， break或break n break是shell的内部命令，用于在循环体