Linux file browsing commands
cat, more, less, head, tail, these five file browsing commands are all external commands.
hann@HannYang:~$ which cat
/usr/bin/cat
hann@HannYang:~$ which more
/usr/bin/more
hann@HannYang:~$ which less
/usr/bin/less
hann@HannYang:~$ which head
/usr/bin/head
hann@HannYang:~$ which tail
/usr/bin/tail(4) head
English help
NAME
head - output the first part of files
SYNOPSIS
head [OPTION]... [FILE]...
DESCRIPTION
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.
AUTHOR
Written by David MacKenzie and Jim Meyering.
REPORTING BUGS
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report head translation bugs to <https://translationproject.org/team/>
COPYRIGHT
Copyright © 2018 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
tail(1)
Full documentation at: <https://www.gnu.org/software/coreutils/head>
or available locally via: info '(coreutils) head invocation'
Chinese notes
head [parameter] filename - display the first few lines of the file
Parameter options:
-n num: Display the first num lines of the file.
-c num: Display the characters of the first num bytes of the file, num can use K, KB, M, MB and other quantitative units.
By default, head displays the first 10 lines of the file.
-v / -q : Whether to display the file name in the first line.
-z : The line separator is NUL. Generally, head -z myfile is equivalent to cat myfile.
Example:
hann@HannYang:~$ head -n 6 cmds.txt
alias - Define or display aliases.
alias: alias [-p] [name[=value] ... ]
bg - Move jobs to the background.
bg: bg [job_spec ...]
bind - Set Readline key bindings and variables.
bind: bind [-lpsvPSVX] [-m keymap] [-f filename] [-q name] [-u name] [-r keyseq] [-x keyseq:shell-command] [keyseq:readline-function or readline-command]
hann@HannYang:~$ head cmds.txt
alias - Define or display aliases.
alias: alias [-p] [name[=value] ... ]
bg - Move jobs to the background.
bg: bg [job_spec ...]
bind - Set Readline key bindings and variables.
bind: bind [-lpsvPSVX] [-m keymap] [-f filename] [-q name] [-u name] [-r keyseq] [-x keyseq:shell-command] [keyseq:readline-function or readline-command]
break - Exit for, while, or until loops.
break: break [n]
builtin - Execute shell builtins.
builtin: builtin [shell-builtin [arg ...]]
hann@HannYang:~$ head -c 35 cmds.txt
alias - Define or display aliases.
hann@HannYang:~$ head -c 50 cmds.txt
alias - Define or display aliases.
alias: alias [-hann@HannYang:~$ head -c 1K cmds.txt
alias - Define or display aliases.
alias: alias [-p] [name[=value] ... ]
bg - Move jobs to the background.
bg: bg [job_spec ...]
bind - Set Readline key bindings and variables.
bind: bind [-lpsvPSVX] [-m keymap] [-f filename] [-q name] [-u name] [-r keyseq] [-x keyseq:shell-command] [keyseq:readline-function or readline-command]
break - Exit for, while, or until loops.
break: break [n]
builtin - Execute shell builtins.
builtin: builtin [shell-builtin [arg ...]]
caller - Return the context of the current subroutine call.
caller: caller [expr]
case - Execute commands based on pattern matching.
case: case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esac
cd - Change the shell working directory.
cd: cd [-L|[-P [-e]] [-@]] [dir]
command - Execute a simple command or display information about commands.
command: command [-pVv] command [arg ...]
compgen - Display possible completions depending on the options.
compgen: compgen [-abcdefgjksuv] [-o option] [-A action] [-G globpat] [-W wordlist] [-F function] [-C cohann@HannYang:~$ head -c 1KB cmds.txt
alias - Define or display aliases.
alias: alias [-p] [name[=value] ... ]
bg - Move jobs to the background.
bg: bg [job_spec ...]
bind - Set Readline key bindings and variables.
bind: bind [-lpsvPSVX] [-m keymap] [-f filename] [-q name] [-u name] [-r keyseq] [-x keyseq:shell-command] [keyseq:readline-function or readline-command]
break - Exit for, while, or until loops.
break: break [n]
builtin - Execute shell builtins.
builtin: builtin [shell-builtin [arg ...]]
caller - Return the context of the current subroutine call.
caller: caller [expr]
case - Execute commands based on pattern matching.
case: case WORD in [PATTERN [| PATTERN]...) COMMANDS ;;]... esac
cd - Change the shell working directory.
cd: cd [-L|[-P [-e]] [-@]] [dir]
command - Execute a simple command or display information about commands.
command: command [-pVv] command [arg ...]
compgen - Display possible completions depending on the options.
compgen: compgen [-abcdefgjksuv] [-o option] [-A action] [-G globpat] [-W wordlishann@HannYang:~$ head -v cmds.txt
==> cmds.txt <==
alias - Define or display aliases.
alias: alias [-p] [name[=value] ... ]
bg - Move jobs to the background.
bg: bg [job_spec ...]
bind - Set Readline key bindings and variables.
bind: bind [-lpsvPSVX] [-m keymap] [-f filename] [-q name] [-u name] [-r keyseq] [-x keyseq:shell-command] [keyseq:readline-function or readline-command]
break - Exit for, while, or until loops.
break: break [n]
builtin - Execute shell builtins.
builtin: builtin [shell-builtin [arg ...]]
Note the difference:
The difference between -c 35 and -c 50, the former happens to end with a newline.
The difference between -c 1K and -c 1KB, the former is 1024 and the latter is 1000; the difference between M and MB, G and GB is the same.
--help brief help
hann@HannYang:~$ head --help
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: <https://www.gnu.org/software/coreutils/>
Report head translation bugs to <https://translationproject.org/team/>
Full documentation at: <https://www.gnu.org/software/coreutils/head>
or available locally via: info '(coreutils) head invocation'--version version number
hann@HannYang:~$ head --version
head (GNU coreutils) 8.30
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Written by David MacKenzie and Jim Meyering.(5) tail
English help
NAME
tail - output the last part of files
SYNOPSIS
tail [OPTION]... [FILE]...
DESCRIPTION
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.
AUTHOR
Written by Paul Rubin, David MacKenzie, Ian Lance Taylor, and Jim Meyering.
REPORTING BUGS
GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Report tail translation bugs to <https://translationproject.org/team/>
COPYRIGHT
Copyright © 2018 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
head(1)
Full documentation at: <https://www.gnu.org/software/coreutils/tail>
or available locally via: info '(coreutils) tail invocation'
Chinese notes
tail [parameter] file name - display the last few lines of the file
Parameter options:
-n num: display the last num lines of the file.
-c num: Display num bytes of characters at the end of the file.
The tail command is the opposite of the head command, it displays the end of the file.
By default, the tail command displays the last 10 lines of the file
These two parameters are basically the same as head, as well as -q -v -z.
The tail command also has several more parameters: -f -s --pid --retry and so on.
-f: This parameter is used to monitor files in real time and output the latest content. For example, tail -f -n 10 /var/log/syslog means to monitor the last 10 lines of the /var/log/syslog file in real time and output the latest content.
-s or --sleep-interval: This parameter is used to specify the sleep time between each output file content. For example, tail -f -s 2 means to sleep for 2 seconds between each output of the file contents.
--pid: This parameter is used to specify the process number (PID) to be monitored. For example, tail -f --pid 12345 means to monitor the process with process number 12345.
--retry: This parameter is used to continue monitoring after the monitored process restarts. For example, tail -f --pid 12345 --retry indicates to continue monitoring after the process restarts.
--help brief help
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: <https://www.gnu.org/software/coreutils/>
Report tail translation bugs to <https://translationproject.org/team/>
Full documentation at: <https://www.gnu.org/software/coreutils/tail>
or available locally via: info '(coreutils) tail invocation'--version version number
hann@HannYang:~$ tail --version
tail (GNU coreutils) 8.30
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Written by Paul Rubin, David MacKenzie, Ian Lance Taylor,
and Jim Meyering.Related Reading:
File browsing of Linux terminal commands (1) cat_Hann Yang's Blog - CSDN Blog
File browsing of Linux terminal commands (2) more_Hann Yang's Blog-CSDN Blog
File browsing of Linux terminal commands (3) less_Hann Yang's Blog-CSDN Blog