BASH-学习笔记

BASH

/bin/bash -c "sudo -u $user $prog"

执行一条命令

READ 命令是BASH程序内建命令，所以man 1 read是没有的。

read 命令

参数选项：

read [-ers] [-a aname] [-d delim] [-i text] [-n nchars] [-N nchars] [-
p prompt] [-t timeout] [-u fd] [name ...]
One line is read from the standard input, or from the file descriptor fd supplied
as an argument to the ‘-u’ option, and the first word is assigned to the first
name, the second word to the second name, and so on, with leftover words and
their intervening separators assigned to the last name. If there are fewer words
read from the input stream than names, the remaining names are assigned
empty values. The characters in the value of the IFS variable are used to split 

the line into words. The backslash character ‘\’ may be used to remove any
special meaning for the next character read and for line continuation. If no
names are supplied, the line read is assigned to the variable REPLY. The return
code is zero, unless end-of-file is encountered, read times out (in which case the
return code is greater than 128), or an invalid file descriptor is supplied as the
argument to ‘-u’.
Options, if supplied, have the following meanings:
-a aname The words are assigned to sequential indices of the array variable
aname, starting at 0. All elements are removed from aname before
the assignment. Other name arguments are ignored.
-d delim The first character of delim is used to terminate the input line,
rather than newline.
-e Readline (see Chapter 8 [Command Line Editing], page 93) is used
to obtain the line. Readline uses the current (or default, if line
editing was not previously active) editing settings.
-i text If Readline is being used to read the line, text is placed into the
editing buffer before editing begins.
-n nchars read returns after reading nchars characters rather than waiting
for a complete line of input, but honor a delimiter if fewer than
nchars characters are read before the delimiter.
-N nchars read returns after reading exactly nchars characters rather than
waiting for a complete line of input, unless EOF is encountered or
read times out. Delimiter characters encountered in the input are
not treated specially and do not cause read to return until nchars
characters are read.
-p prompt Display prompt, without a trailing newline, before attempting to
read any input. The prompt is displayed only if input is coming
from a terminal.
-r If this option is given, backslash does not act as an escape character.
The backslash is considered to be part of the line. In particular, a
backslash-newline pair may not be used as a line continuation.
-s Silent mode. If input is coming from a terminal, characters are not
echoed.
-t timeout
Cause read to time out and return failure if a complete line of input
is not read within timeout seconds. timeout may be a decimal
number with a fractional portion following the decimal point. This
option is only effective if read is reading input from a terminal,
pipe, or other special file; it has no effect when reading from regular
files. If timeout is 0, read returns success if input is available on
the specified file descriptor, failure otherwise. The exit status is
greater than 128 if the timeout is exceeded.

-u fd Read input from file descriptor fd.