[命令集3.3]FreeBSD下的启动引导
如果新内核不能引导,要引导一个旧内核,停止启动倒计时,做如下动作:
# unload # load kernel.old # boot |
[linux秘笈27]Diff命令
diff命令，通常用来比较两个文件的差别，命令的输出比较隐晦，不能直接阅读。使用方法
Syntax: diff [options] file1 file2 |
具体的使用方法
jcai@jcai-notebook:~$ diff --help Usage: diff [OPTION]... FILES Compare files line by line. -i --ignore-case Ignore case differences in file contents. --ignore-file-name-case Ignore case when comparing file names. --no-ignore-file-name-case Consider case when comparing file names. -E --ignore-tab-expansion Ignore changes due to tab expansion. -b --ignore-space-change Ignore changes in the amount of white space. -w --ignore-all-space Ignore all white space. -B --ignore-blank-lines Ignore changes whose lines are all blank. -I RE --ignore-matching-lines=RE Ignore changes whose lines all match RE. --strip-trailing-cr Strip trailing carriage return on input. -a --text Treat all files as text. -c -C NUM --context[=NUM] Output NUM (default 3) lines of copied context. -u -U NUM --unified[=NUM] Output NUM (default 3) lines of unified context. --label LABEL Use LABEL instead of file name. -p --show-c-function Show which C function each change is in. -F RE --show-function-line=RE Show the most recent line matching RE. -q --brief Output only whether files differ. -e --ed Output an ed script. --normal Output a normal diff. -n --rcs Output an RCS format diff. -y --side-by-side Output in two columns. -W NUM --width=NUM Output at most NUM (default 130) print columns. --left-column Output only the left column of common lines. --suppress-common-lines Do not output common lines. -D NAME --ifdef=NAME Output merged file to show `#ifdef NAME' diffs. --GTYPE-group-format=GFMT Similar, but format GTYPE input groups with GFMT. --line-format=LFMT Similar, but format all input lines with LFMT. --LTYPE-line-format=LFMT Similar, but format LTYPE input lines with LFMT. LTYPE is `old', `new', or `unchanged'. GTYPE is LTYPE or `changed'. GFMT may contain: %< lines from FILE1 %> lines from FILE2 %= lines common to FILE1 and FILE2 %[-][WIDTH][.[PREC]]{doxX}LETTER printf-style spec for LETTER LETTERs are as follows for new group, lower case for old group: F first line number L last line number N number of lines = L-F+1 E F-1 M L+1 LFMT may contain: %L contents of line %l contents of line, excluding any trailing newline %[-][WIDTH][.[PREC]]{doxX}n printf-style spec for input line number Either GFMT or LFMT may contain: %% % %c'C' the single character C %c'\OOO' the character with octal code OOO -l --paginate Pass the output through `pr' to paginate it. -t --expand-tabs Expand tabs to spaces in output. -T --initial-tab Make tabs line up by prepending a tab. -r --recursive Recursively compare any subdirectories found. -N --new-file Treat absent files as empty. --unidirectional-new-file Treat absent first files as empty. -s --report-identical-files Report when two files are the same. -x PAT --exclude=PAT Exclude files that match PAT. -X FILE --exclude-from=FILE Exclude files that match any pattern in FILE. -S FILE --starting-file=FILE Start with FILE when comparing directories. --from-file=FILE1 Compare FILE1 to all operands. FILE1 can be a directory. --to-file=FILE2 Compare all operands to FILE2. FILE2 can be a directory. --horizon-lines=NUM Keep NUM lines of the common prefix and suffix. -d --minimal Try hard to find a smaller set of changes. --speed-large-files Assume large files and many scattered small changes. -v --version Output version info. --help Output this help. FILES are `FILE1 FILE2' or `DIR1 DIR2' or `DIR FILE...' or `FILE... DIR'. If --from-file or --to-file is given, there are no restrictions on FILES. If a FILE is `-', read standard input. |
当用我的新文件去和老文件比较那些发生了修改？
当执行比较的时候，在diff命令中使用选项 -w 能够忽略掉空格，
查看diff输出时候的注意是：
- ‘—’ 线上面的是第一个文件发生的变化
- ‘—’线向下的第二个文件发生的变化
- < 符号表示的内容，属于第一个文件，>符号表示的内容属于第二个文件
jcai@jcai-notebook:~/tmp$ cat test.txt 我们 你们现在还好吗？比较文本 jcai@jcai-notebook:~/tmp$ cat test2.txt 他们 我们 你们现在还好吗？ jcai@jcai-notebook:~/tmp$ diff test.txt test2.txt 0a1 > 他们 2c3 < 你们现在还好吗？比较文本 --- > 你们现在还好吗？ |
[命令集3.2]Linux下和磁盘相关的命令
# diskinfo -v /dev/ad2 # 显示磁盘信息(扇区/大小) (FreeBSD) # hdparm -I /dev/sda # 显示 IDE/ATA 磁盘信息 (Linux) # fdisk /dev/ad2 # 显示和修改磁盘分区表 # smartctl -a /dev/ad2 # 显示磁盘检测信息 |
[linux秘笈26]Stat命令
Stat命令被用来查看单个文件或者文件系统的状态以及属性。
显示某一个文件或者文件系统的状态
jcai@jcai-notebook:~$ stat /etc/mysql/my.cnf File: `/etc/mysql/my.cnf' Size: 3978 Blocks: 8 IO Block: 4096 regular file Device: 802h/2050d Inode: 449073 Links: 1 Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2009-03-18 21:31:03.000000000 +0800 Modify: 2009-03-04 18:08:03.000000000 +0800 Change: 2009-03-04 18:08:03.000000000 +0800 jcai@jcai-notebook:~$ stat /home/jcai File: `/home/jcai' Size: 4096 Blocks: 8 IO Block: 4096 directory Device: fe00h/65024d Inode: 2187265 Links: 66 Access: (0755/drwxr-xr-x) Uid: ( 1000/ jcai) Gid: ( 1000/ jcai) Access: 2009-03-19 08:14:47.000000000 +0800 Modify: 2009-03-19 09:22:12.000000000 +0800 Change: 2009-03-19 09:22:12.000000000 +0800 |
使用 -f 选项来战士文件系统的状态
jcai@jcai-notebook:~$ stat -f / File: "/" ID: f346283e2da86295 Namelen: 255 Type: ext2/ext3 Block size: 4096 Fundamental block size: 4096 Blocks: Total: 4845177 Free: 3879940 Available: 3635752 Inodes: Total: 1224000 Free: 1082670 |
[命令集3.1]linux文件的权限
用 chmod 和 chown 更改访问权限和所有权。对于所有用户的默认掩码(umask)可以在 /etc/profile (Linux)
或 /etc/login.conf (FreeBSD) 中修改。其默认掩码(umask)通常为 022。掩码可以和777做减法,从而得到755
的权限。
1 –x 执行 # Mode 764 = 执行/读/写 | 读/写 | 读
2 -w- 写 # |—所有者|—用户组|—其他用户|
4 r– 读
ugo=a u=所有者, g=用户组, o=其他用户, a=所有用户
# chmod [OPTION] MODE[,MODE] FILE # MODE 可以是 [ugoa]*([-+=]([rwxXst])) # chmod 640 /var/log/maillog # 更改 maillog 访问权限为 -rw-r----- # chmod u=rw,g=r,o= /var/log/maillog # 同上 # chmod -R o-r /home/* # 递归去除所有其他用户的可读权限 在可执行位设置 SUID (知道你在干什么!13) # chmod u+s /path/to/prog # # find / -perm -u+s -print # 查找所有设置过 SUID 位的程序 # chown user:group /path/to/file # 改变文件的所有者和文件关联的组 # chgrp group /path/to/file # 改变文件关联的组 # chmod 640 `find ./ -type f -print` # Change permissions to 640 for all files # chmod 751 `find ./ -type d -print` # Change permissions to 751 for all directories |
Linux秘笈25.Linux的Cut命令
Cut command can be used to display only specific columns from a text file or
other command outputs.
Following are some of the examples.
Display the 1st field (employee name) from a colon delimited file
$ cut -d: -f 1 names.txt Emma Thomas Alex Jason Madison Randy Sanjay Gupta Nisha Singh |
Display 1st and 3rd field from a colon delimited file
$ cut -d: -f 1,3 names.txt Emma Thomas:Marketing Alex Jason:Sales Madison Randy:Product Development Sanjay Gupta:Support Nisha Singh:Sales |
Display only the first 8 characters of every line in a file
$ cut -c 1-8 names.txt Emma Tho Alex Jas Madison Sanjay G Nisha Si |
Linux秘笈24. Uniq命令
Uniq command is mostly used in combination with sort command, as uniq
removes duplicates only from a sorted file. i.e In order for uniq to work, all
the duplicate entries should be in the adjacent lines. Following are some
common examples.
1. When you have an employee file with duplicate entries, you can do the
following to remove duplicates.
$ sort namesd.txt | uniq $ sort –u namesd.txt |
2. If you want to know how many lines are duplicates, do the following. The
first field in the following examples indicates how many duplicates where
found for that particular line. So, in this example the lines beginning with
Alex and Emma were found twice in the namesd.txt file.
$ sort namesd.txt | uniq –c 2 Alex Jason:200:Sales 2 Emma Thomas:100:Marketing 1 Madison Randy:300:Product Development 1 Nisha Singh:500:Sales 1 Sanjay Gupta:400:Support |
3. The following displays only the entries that are duplicates.
$ sort namesd.txt | uniq –cd 2 Alex Jason:200:Sales 2 Emma Thomas:100:Marketing |
Kill命令与信号
使用kill 或killall 终止或发送一个信号给进程。
# ping -i 60 cb.vu > ping.log &
[1] 4712
# kill -s TERM 4712 # 同 kill -15 4712
# killall -1 httpd # 发送 HUP 信号终止进程 httpd
# pkill -9 http # 发送 TERM 信号终止包含 http 的进程
# pkill -TERM -u www # 发送 TERM 信号终止 www 所有者进程
# fuser -k -TERM -m /home # 终止所有访问 /home 的进程(卸载该分区前)
下面是一些重要的信号：
1 HUP (挂起)
2 INT (中断)
3 QUIT (退出)
9 KILL (KILL 信号不能被捕捉，不能被忽略。)
15 TERM (软件终止信号)
Linux秘笈23.Sort命令
Sort命令能够对一个文本文件的行进行排序,下面的几个实用的样例展示怎么去对样例文本进行排序。样例文本的格式为：employee_name:employee_id:department_name.
$ cat names.txt Emma Thomas:100:Marketing Alex Jason:200:Sales Madison Randy:300:Product Development Sanjay Gupta:400:Support Nisha Singh:500:Sales |
以一个升序排列文本文件
$ sort names.txt Alex Jason:200:Sales Emma Thomas:100:Marketing Madison Randy:300:Product Development Nisha Singh:500:Sales Sanjay Gupta:400:Support |
以倒序排列文本文件
$ sort -r names.txt Sanjay Gupta:400:Support Nisha Singh:500:Sales Madison Randy:300:Product Development Emma Thomas:100:Marketing Alex Jason:200:Sales
用第二字段排列一个以冒号分隔的文本文件
$ sort -t: -k 2 names.txt Emma Thomas:100:Marketing Alex Jason:200:Sales Madison Randy:300:Product Development Sanjay Gupta:400:Support Nisha Singh:500:Sales |
以第三个字段排列一个以tab分隔的文本文件，并且禁止重复
$ sort -t: -u -k 3 names.txt Emma Thomas:100:Marketing adison Randy:300:Product Development Alex Jason:200:Sales Sanjay Gupta:400:Support |
通过ip地址来排序/etc/hosts文件
$ sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n /etc/hosts 127.0.0.1 localhost.localdomain localhost 192.168.100.101 dev-db.thegeekstuff.com dev-db 192.168.100.102 prod-db.thegeekstuff.com prod-db 192.168.101.20 dev-web.thegeekstuff.com dev-web 192.168.101.21 prod-web.thegeekstuff.com prod-web |
合并sort和其他命令
ps –ef | sort : Sort the output of process list ls -al | sort +4n : List the files in the ascending order of the file-size. i.e sorted by 5th filed and displaying smallest files first. ls -al | sort +4nr : List the files in the descending order of the file-size. i.e sorted by 5th filed and displaying largest files first. |
Linux秘笈22. Xargs命令
xargs是一个强有力的命令，它能够捕获一个命令的输出，然后传递给另外一个命令，下面是一些如何有效使用xargs的实用例子。
1. 当你尝试用rm删除太多的文件，你可能得到一个错误信息：/bin/rm Argument list too long. 用xargs去避免这个问题。
find ~ -name ‘*.log’ -print0 | xargs -0 rm -f
2. 获得/etc/下所有*.conf结尾的文件列表，有几种不同的方法能得到相同的结果，下面的例子仅仅是示范怎么实用xargs，在这个例子中实用xargs将find命令的输出传递给ls -l
# find /etc -name "*.conf" | xargs ls –l |
3. 假如你有一个文件包含了很多你希望下载的URL,你能够使用xargs下载所有链接。
# cat url-list.txt | xargs wget –c |
4. 查找所有的jpg文件，并且压缩他。
# find / -name *.jpg -type f -print | xargs tar -cvzf images.tar.gz |
5. 拷贝所有的图片文件到一个外部的硬盘驱动
# ls *.jpg | xargs -n1 -i cp {} /external-hard-drive/directory |
