Linux Manuals

dup, dup2, dup3 – duplicate a file descriptor Synopsis#include <unistd.h> int dup(int oldfd); int dup2(int oldfd, int newfd); #define _GNU_SOURCE /* See feature_test_macros(7) */ #include <fcntl.h> /* Obtain O_* constant definitions */ #include <unistd.h> int dup3(int oldfd, int newfd, int flags);DescriptionThe dup() system call creates a copy of the file descriptor oldfd, using the lowest-numbered…

close – close a file descriptor Synopsis#include <unistd.h> int close(int fd);Descriptionclose() closes a file descriptor, so that it no longer refers to any file and may be reused. Any record locks (see fcntl(2)) held on the file it was associated with, and owned by the process, are removed (regardless of the file descriptor that was…

sort – sort lines of text files Synopsissort [,OPTION/]… [,FILE/]… sort [,OPTION/]… ,–files0-from=F/ DescriptionWrite sorted concatenation of all FILE(s) to standard output. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. Ordering options: -b, –ignore-leading-blanks ignore leading blanks -d, –dictionary-order consider only…

rm – remove files or directories Synopsisrm [,OPTION/]… [,FILE/]… DescriptionThis manual page documents the GNU version of rm. rm removes each specified file. By default, it does not remove directories. If the -I or –interactive=once option is given, and there are more than three files or the -r, -R, or –recursive are given, then rm…

ps – report a snapshot of the current processes. Synopsisps [,options/] Descriptionps displays information about a selection of the active processes. If you want a repetitive update of the selection and the displayed information, use top instead. This version of ps accepts several kinds of options: 1 UNIX options, which may be grouped and must…

mv – move (rename) files Synopsismv [,OPTION/]… [,-T/] ,SOURCE DEST/ mv [,OPTION/]… ,SOURCE/… ,DIRECTORY/ mv [,OPTION/]… ,-t DIRECTORY SOURCE/… DescriptionRename SOURCE to DEST, or move SOURCE(s) to DIRECTORY. Mandatory arguments to long options are mandatory for short options too. –backup[=,CONTROL/] make a backup of each existing destination file -b like –backup but does not accept…

mkdir – make directories Synopsismkdir [,OPTION/]… ,DIRECTORY/… DescriptionCreate the DIRECTORY(ies), if they do not already exist. Mandatory arguments to long options are mandatory for short options too. -m, –mode=,MODE/ set file mode (as in chmod), not a=rwx – umask -p, –parents no error if existing, make parent directories as needed -v, –verbose print a message…

less – opposite of more Synopsisless -? less –help less -V less –version less [-[+]aABcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~] [-b space/] [-h lines/] [-j line/] [-k keyfile/] [-{oO} logfile/] [-p pattern/] [-P prompt/] [-t tag/] [-T tagsfile/] [-x tab/,…] [-y lines/] [-[z] lines/] [-# shift/] [+[+]cmd/] [–] [filename/]… (See the OPTIONS section for alternate option syntax with long option…

kill – send a signal to a process Synopsiskill [options] <pid> […] DescriptionThe default signal for kill is TERM. Use -l or -L to list available signals. Particularly useful signals include HUP, INT, KILL, STOP, CONT, and 0. Alternate signals may be specified in three ways: -9, -SIGKILL or -KILL. Negative PID values may be…

lwp-request, GET, POST, HEAD – Simple command line user agent Synopsislwp-request [-afPuUsSedvhx] [-m method] [-b base URL] [-t timeout]       [-i if-modified-since] [-c content-type]       [-C credentials] [-p proxy-url] [-o format] url… DescriptionThis program can be used to send requests to WWW servers and your local file system. The request content for POST and PUT methods is read from stdin. The content of the response is…

gzip, gunzip, zcat – compress or expand files Synopsisgzip [ -acdfhklLnNrtvV19 ] [-S suffix] [ name … ] gunzip [ -acfhklLnNrtvV ] [-S suffix] [ name … ] zcat [ -fhLV ] [ name … ] DescriptionGzip reduces the size of the named files using Lempel-Ziv coding (LZ77). Whenever possible, each file is replaced by…

find – search for files in a directory hierarchy Synopsisfind [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point…] [expression] DescriptionThis manual page documents the GNU version of find. GNU find searches the directory tree rooted at each given starting-point by evaluating the given expression from left to right, according to the rules of precedence (see section…

diff – compare files line by line Synopsisdiff [OPTION]… FILES DescriptionCompare FILES line by line. Mandatory arguments to long options are mandatory for short options too. –normal output a normal diff (the default) -q, –brief report only when files differ -s, –report-identical-files report when two files are the same -c, -C NUM, –context[=NUM] output NUM…

date – print or set the system date and time Synopsisdate [,OPTION/]… [,+FORMAT/] date [,-u|–utc|–universal/] [,MMDDhhmm/[[,CC/],YY/][,.ss/]] DescriptionDisplay the current time in the given FORMAT, or set the system date. Mandatory arguments to long options are mandatory for short options too. -d, –date=,STRING/ display time described by STRING, not ‘now’ –debug annotate the parsed date, and…

cp – copy files and directories Synopsiscp [,OPTION/]… [,-T/] ,SOURCE DEST/ cp [,OPTION/]… ,SOURCE/… ,DIRECTORY/ cp [,OPTION/]… ,-t DIRECTORY SOURCE/… DescriptionCopy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY. Mandatory arguments to long options are mandatory for short options too. -a, –archive same as -dR –preserve=,all/ –attributes-only don’t copy the file data, just the attributes…

chmod – change file mode bits Synopsischmod [,OPTION/]… ,MODE/[,,MODE/]… ,FILE/… chmod [,OPTION/]… ,OCTAL-MODE FILE/… chmod [,OPTION/]… ,–reference=RFILE FILE/… DescriptionThis manual page documents the GNU version of chmod. chmod changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number…

bash – GNU Bourne-Again SHell Synopsisbash [options] [command_string | file] CopyrightBash is Copyright (C) 1989-2020 by the Free Software Foundation, Inc. DescriptionBash is an sh-compatible command language interpreter that executes commands read from the standard input or from a file. Bash also incorporates useful features from the Korn and C shells (ksh and csh). Bash…

strcpy, strncpy – copy a string Synopsis #include <string.h> char *strcpy(char *dest, const char *src); char *strncpy(char *dest, const char *src, size_t n); Description The strcpy() function copies the string pointed to by src, including the terminating null byte (‘\0’), to the buffer pointed to by dest. The strings may not overlap, and the destination…

write – write to a file descriptor Synopsis#include <unistd.h> ssize_t write(int fd, const void *buf, size_t count); Descriptionwrite() writes up to count bytes from the buffer starting at buf to the file referred to by the file descriptor fd. The number of bytes written may be less than count if, for example, there is insufficient…

read – read from a file descriptor Synopsis#include <unistd.h> ssize_t read(int fd, void *buf, size_t count);Descriptionread() attempts to read up to count bytes from file descriptor fd into the buffer starting at buf. On files that support seeking, the read operation commences at the file offset, and the file offset is incremented by the number…