8.2. 捕获用户输入

michel ~> ls -l /dev/std*
lrwxrwxrwx  1 root    root     17 Oct  2 07:46 /dev/stderr -> ../proc/self/fd/2
lrwxrwxrwx  1 root    root     17 Oct  2 07:46 /dev/stdin -> ../proc/self/fd/0
lrwxrwxrwx  1 root    root     17 Oct  2 07:46 /dev/stdout -> ../proc/self/fd/1

michel ~> ls -l /proc/self/fd/[0-2]
lrwx------  1 michel  michel   64 Jan 23 12:11 /proc/self/fd/0 -> /dev/pts/6
lrwx------  1 michel  michel   64 Jan 23 12:11 /proc/self/fd/1 -> /dev/pts/6
lrwx------  1 michel  michel   64 Jan 23 12:11 /proc/self/fd/2 -> /dev/pts/6

michel ~> date
Fri Jan 24 11:05:50 CET 2003

michel ~> at 1107
warning: commands will be executed using (in order) 
a) $SHELL b) login shell c)/bin/sh
at> ls -l /proc/self/fd/ > /var/tmp/fdtest.at
at> <EOT>
job 10 at 2003-01-24 11:07

michel ~> cat /var/tmp/fdtest.at
total 0
lr-x------    1 michel michel  64 Jan 24 11:07 0 -> /var/spool/at/!0000c010959eb (deleted)
l-wx------    1 michel michel  64 Jan 24 11:07 1 -> /var/tmp/fdtest.at
l-wx------    1 michel michel  64 Jan 24 11:07 2 -> /var/spool/at/spool/a0000c010959eb
lr-x------    1 michel michel  64 Jan 24 11:07 3 -> /proc/21949/fd

michel ~> crontab -l
# DO NOT EDIT THIS FILE - edit the master and reinstall.
# (/tmp/crontab.21968 installed on Fri Jan 24 11:30:41 2003)
# (Cron version -- $Id: chap8.xml,v 1.9 2006/09/28 09:42:45 tille Exp $)
32 11 * * * ls -l /proc/self/fd/ > /var/tmp/fdtest.cron

michel ~> cat /var/tmp/fdtest.cron
total 0
lr-x------    1 michel michel  64 Jan 24 11:32 0 -> pipe:[124440]
l-wx------    1 michel michel  64 Jan 24 11:32 1 -> /var/tmp/fdtest.cron
l-wx------    1 michel michel  64 Jan 24 11:32 2 -> pipe:[124441]
lr-x------    1 michel michel  64 Jan 24 11:32 3 -> /proc/21974/fd

ls -l * 2> /var/tmp/unaccessible-in-spool

ls -l * > /var/tmp/spoollist 2>&1

ls -l * 2 >& 1 > /var/tmp/spoollist

michel ~> filter body.txt.gz | cat header.txt - footer.txt
This text is printed at the beginning of each print job and thanks the sysadmin
for setting us up such a great printing infrastructure.

Text to be filtered.

This text is printed at the end of each print job.

michel ~> filter body.txt | cat header.txt /dev/fd/0 footer.txt | lp

michel ~> cat listdirs.sh
#!/bin/bash

# This script prints standard output unchanged, while standard error is 
# redirected for processing by awk.

INPUTDIR="$1"

# fd 6 targets fd 1 target (console out) in current shell
exec 6>&1

# fd 1 targets pipe, fd 2 targets fd 1 target (pipe),
# fd 1 targets fd 6 target (console out), fd 6 closed, execute ls
ls "$INPUTDIR"/* 2>&1 >&6 6>&- \
				# Closes fd 6 for awk, but not for ls.

| awk 'BEGIN { FS=":" } { print "YOU HAVE NO ACCESS TO" $2 }' 6>&-

# fd 6 closed for current shell
exec 6>&-

michel ~> cat startsurf.sh
#!/bin/bash

# This script provides an easy way for users to choose between browsers.

echo "These are the web browsers on this system:"
 
# Start here document
cat << BROWSERS
mozilla
links
lynx
konqueror
opera
netscape
BROWSERS
# End here document

echo -n "Which is your favorite? "
read browser

echo "Starting $browser, please wait..."
$browser &

michel ~> startsurf.sh
These are the web browsers on this system:
mozilla
links
lynx
konqueror
opera
netscape
Which is your favorite? opera
Starting opera, please wait...

#!/bin/bash
 
# This script installs packages automatically, using yum.
 
if [ $# -lt 1 ]; then
        echo "Usage: $0 package."
        exit 1
fi
 
yum install $1 << CONFIRM
y
CONFIRM

[root@picon bin]# ./install.sh tuxracer
Gathering header information file(s) from server(s)
Server: Fedora Linux 2 - i386 - core
Server: Fedora Linux 2 - i386 - freshrpms
Server: JPackage 1.5 for Fedora Core 2
Server: JPackage 1.5, generic
Server: Fedora Linux 2 - i386 - updates
Finding updated packages
Downloading needed headers
Resolving dependencies
Dependencies resolved
I will do the following:
[install: tuxracer 0.61-26.i386]
Is this ok [y/N]: EnterDownloading Packages
Running test transaction:
Test transaction complete, Success!
tuxracer 100 % done 1/1
Installed:  tuxracer 0.61-26.i386
Transaction(s) Complete