SysTutorials Posts

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

NAME find – search for files in a directory hierarchy SYNOPSIS find [-H] [-L] [-P] [-D debugopts] [-Olevel] [starting-point…] [expression] DESCRIPTION This 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…

NAME diff – compare files line by line SYNOPSIS diff [OPTION]… FILES DESCRIPTION Compare 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,…

NAME date – print or set the system date and time SYNOPSIS date [,OPTION/]… [,+FORMAT/] date [,-u|–utc|–universal/] [,MMDDhhmm/[[,CC/],YY/][,.ss/]] DESCRIPTION Display 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…

NAME cp – copy files and directories SYNOPSIS cp [,OPTION/]… [,-T/] ,SOURCE DEST/ cp [,OPTION/]… ,SOURCE/… ,DIRECTORY/ cp [,OPTION/]… ,-t DIRECTORY SOURCE/… DESCRIPTION Copy 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,…

NAME chmod – change file mode bits SYNOPSIS chmod [,OPTION/]… ,MODE/[,,MODE/]… ,FILE/… chmod [,OPTION/]… ,OCTAL-MODE FILE/… chmod [,OPTION/]… ,–reference=RFILE FILE/… DESCRIPTION This 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…

NAME bash – GNU Bourne-Again SHell SYNOPSIS bash [options] [command_string | file] COPYRIGHT Bash is Copyright (C) 1989-2020 by the Free Software Foundation, Inc. DESCRIPTION Bash 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…

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…

NAME write – write to a file descriptor SYNOPSIS #include <unistd.h> ssize_t write(int fd, const void *buf, size_t count); DESCRIPTION write() 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,…

NAME read – read from a file descriptor SYNOPSIS #include <unistd.h> ssize_t read(int fd, void *buf, size_t count); DESCRIPTION read() 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…

NAME cat – concatenate files and print on the standard output SYNOPSIS cat [,OPTION/]… [,FILE/]… DESCRIPTION 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…

NAME stat, fstat, lstat, fstatat – get file status SYNOPSIS #include <sys/stat.h> #include <sys/types.h> #include <unistd.h> int stat(const char *pathname, struct stat *statbuf); int fstat(int fd, struct stat *statbuf); int lstat(const char *pathname, struct stat *statbuf); #include <fcntl.h> /* Definition of AT_* constants */ #include <sys/stat.h> int fstatat(int dirfd, const char *pathname, struct stat *statbuf,…

NAME grep, egrep, fgrep, rgrep – print lines that match patterns SYNOPSIS grep [OPTION…] PATTERNS [FILE…] grep [OPTION…] -e PATTERNS … [FILE…] grep [OPTION…] -f PATTERN_FILE … [FILE…] DESCRIPTION grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated by newline characters, and grep prints each line that matches a pattern….

NAME malloc, free, calloc, realloc, reallocarray – allocate and free dynamic memory SYNOPSIS #include <stdlib.h> void *malloc(size_t size); void free(void *ptr); void *calloc(size_t nmemb, size_t size); void *realloc(void *ptr, size_t size); void *reallocarray(void *ptr, size_t nmemb, size_t size); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): reallocarray():     Since glibc 2.29:         _DEFAULT_SOURCE     Glibc 2.28 and earlier:…

printf, fprintf, dprintf, sprintf, snprintf, vprintf, vfprintf, vdprintf, vsprintf, vsnprintf – formatted output conversion Synopsis#include <stdio.h> int printf(const char *format, …); int fprintf(FILE *stream, const char *format, …); int dprintf(int fd, const char *format, …); int sprintf(char *str, const char *format, …); int snprintf(char *str, size_t size, const char *format, …); #include <stdarg.h> int vprintf(const…

NAME open, openat, creat – open and possibly create a file SYNOPSIS #include <fcntl.h> #include <sys/stat.h> #include <sys/types.h> int open(const char *pathname, int flags); int open(const char *pathname, int flags, mode_t mode); int creat(const char *pathname, mode_t mode); int openat(int dirfd, const char *pathname, int flags); int openat(int dirfd, const char *pathname, int flags, mode_t…

NAME ls – list directory contents SYNOPSIS ls [,OPTION/]… [,FILE/]… DESCRIPTION List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor –sort is specified. Mandatory arguments to long options are mandatory for short options too. -a, –all do not ignore entries starting with . -A, –almost-all do…