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Linux文本查看命令及其选项详解(cat,head,tail)

linux系统内置命令可以通过以下两种方式查询:“cat –help” 或者“man cat”。

cat命令的常用选项和官方解释如下:

cat file_name 显示文件全部内容

cat -b file_name 显示文件非空行内容

cat -E file_name 在文件每行末尾显示$,常用于管道功能

cat -n file_name 显示内容和行号

Usage: cat [OPTION]... [FILE]... Concatenate FILE(s) to standard output.  With no FILE, or when FILE is -, read standard input.    -A, --show-all           equivalent to -vET   -b, --number-nonblank    number nonempty output lines, overrides -n   -e                       equivalent to -vE   -E, --show-ends          display $ at end of each line   -n, --number             number all output lines   -s, --squeeze-blank      suppress repeated empty output lines   -t                       equivalent to -vT   -T, --show-tabs          display TAB characters as ^I   -u                       (ignored)   -v, --show-nonprinting   use ^ and M- notation, except for LFD and TAB       --help     display this help and exit       --version  output version information and exit  Examples:   cat f - g  Output f's contents, then standard input, then g's contents.   cat        Copy standard input to standard output.  GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Full documentation at: <http://www.gnu.org/software/coreutils/cat>

head命令及其选项如下:

head -c10 file_name 显示一开始的10个字节

head -c-10 file_name 显示除末尾10个字节之外的内容

head -n10 file_name 显示一开始的10行内容

head -n-10 file_name 显示除末尾的10行之外的内容

Usage: head [OPTION]... [FILE]... Print the first 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name.  With no FILE, or when FILE is -, read standard input.  Mandatory arguments to long options are mandatory for short options too.   -c, --bytes=[-]NUM       print the first NUM bytes of each file;                              with the leading '-', print all but the last                              NUM bytes of each file   -n, --lines=[-]NUM       print the first NUM lines instead of the first 10;                              with the leading '-', print all but the last                              NUM lines of each file   -q, --quiet, --silent    never print headers giving file names   -v, --verbose            always print headers giving file names   -z, --zero-terminated    line delimiter is NUL, not newline       --help     display this help and exit       --version  output version information and exit  NUM may have a multiplier suffix: b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.  GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Full documentation at: <http://www.gnu.org/software/coreutils/head>

tail命令及其选项如下:

tail -c10 file_name 显示末尾的10个字节

tail -c-10 file_name 显示除开头10个字节之外的内容

tail -n10 file_name 显示末尾的10行内容

tail -n-10 file_name 显示除开头的10行之外的内容

Usage: tail [OPTION]... [FILE]... Print the last 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name.  With no FILE, or when FILE is -, read standard input.  Mandatory arguments to long options are mandatory for short options too.   -c, --bytes=[+]NUM       output the last NUM bytes; or use -c +NUM to                              output starting with byte NUM of each file   -f, --follow[={name|descriptor}]                            output appended data as the file grows;                              an absent option argument means 'descriptor'   -F                       same as --follow=name --retry   -n, --lines=[+]NUM       output the last NUM lines, instead of the last 10;                              or use -n +NUM to output starting with line NUM       --max-unchanged-stats=N                            with --follow=name, reopen a FILE which has not                              changed size after N (default 5) iterations                              to see if it has been unlinked or renamed                              (this is the usual case of rotated log files);                              with inotify, this option is rarely useful       --pid=PID            with -f, terminate after process ID, PID dies   -q, --quiet, --silent    never output headers giving file names       --retry              keep trying to open a file if it is inaccessible   -s, --sleep-interval=N   with -f, sleep for approximately N seconds                              (default 1.0) between iterations;                              with inotify and --pid=P, check process P at                              least once every N seconds   -v, --verbose            always output headers giving file names   -z, --zero-terminated    line delimiter is NUL, not newline       --help     display this help and exit       --version  output version information and exit  NUM may have a multiplier suffix: b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.  With --follow (-f), tail defaults to following the file descriptor, which means that even if a tail'ed file is renamed, tail will continue to track its end.  This default behavior is not desirable when you really want to track the actual name of the file, not the file descriptor (e.g., log rotation).  Use --follow=name in that case.  That causes tail to track the named file in a way that accommodates renaming, removal and creation.  GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Full documentation at: <http://www.gnu.org/software/coreutils/tail>

搭配管道使用更佳

此外,这三个命令常常与管道功能搭配,用于文件内容的操作,例如:

对data.txt中的数据进行排序:cat data.txt | sort

对data.txt中的内容匹配:cat data.txt | grep ‘a’

输出data.txt中的非空行数:cat -b data.txt | wc -l


		
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