#! /bin/bash # this is a comment echo "Hello World" # this is also a comment echo Our shell name is $BASH echo Our shell version name is $BASH_VERSION echo Our home directory is $HOME echo Our current working directory is $PWD name=Mark VALUE=10 echo The name is $name echo value $VALUE
Sunday, February 19, 2017
Shell Scripting Tutorial for Beginners 1 - using Variables and Comments
Tuesday, February 14, 2017
Node.js Tutorial for Beginners 23 - using JavaScript with EJS
Project files
index.js
node_modules/
package.json
views/views/students.ejs
var express = require('express'); var app = express(); app.set('view engine', 'ejs'); var students = { 1 : { name : 'Mark', subjects : ['c++', 'Java', 'c'] }, 2 : { name : 'Tom', subjects : ['C#', 'Pthon', 'Mysql'] }, 3 : { name : 'John', subjects : ['Javascript', 'Sqlite', 'c'] }, } app.get('/students/:id', function(req, rep) { rep.render('students', { name : students[req.params.id].name , id : req.params.id , subjects : students[req.params.id].subjects}); }) app.listen(3000, function() { console.log('our server is live on posrt 3000'); })
package.json
{
"name": "express_test",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC",
"dependencies": {
"ejs": "^2.5.5",
"express": "^4.14.1"
}
}
\views\students.ejs
<html> <head> <style> body { background-color: limegreen } </style> </head> <body> <h1>You have requested the student name : <%= name %></h1> <p>id : <%= id %></p> <h1>Subjects</h1> <ul> <% subjects.forEach(function(item) { %> <li> <%= item %></li> <%});%> </ul> </body> </html>
Saturday, February 11, 2017
Node.js Tutorial for Beginners 22 - Node.js template engine EJS in Express
Project files
about.html
index.html
index.js
node_modules/
package.json
views/students.ejs
var express = require('express'); var app = express(); app.set('view engine', 'ejs'); app.get('/', function(req, rep) { rep.sendFile(__dirname + '/index.html'); }) app.get('/about', function(req, rep) { rep.sendFile(__dirname + '/about.html'); }) var students = { 1 : 'Mark', 2 : 'Tom', 3 : 'john' } app.get('/students/:id', function(req, rep) { rep.render('students', { name : students[req.params.id] , id : req.params.id}); }) app.listen(3000, function() { console.log('our server is live on posrt 3000'); })
package.json
{
"name": "express_test",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC",
"dependencies": {
"ejs": "^2.5.5",
"express": "^4.14.1"
}
}
\views\students.ejs
<html> <head> <style> body { background-color: limegreen } </style> </head> <body> <h1>You have requested the student name : <%= name %></h1> <p>id : <%= id %></p> </body> </html>
index.html
<html> <head> <style> body { background-color: limegreen } </style> </head> <body> <h1>Home Page</h1> </body> </html>
about.html
<html> <head> <style> body { background-color: limegreen } </style> </head> <body> <h1>About Page</h1> </body> </html>
Thursday, February 9, 2017
Wednesday, February 8, 2017
Node.js Tutorial for Beginners 21 - Express.js route parameter
var express = require('express'); var app = express(); app.get('/', function(req, rep) { rep.send('this is home page'); }) app.get('/about', function(req, rep) { rep.send('this is about page'); }) app.get('/contect', function(req, rep) { rep.send('this is contect page'); }) var students = { 1 : 'Mark', 2 : 'Tom', 3 : 'john' } app.get('/students/:id', function(req, rep) { rep.send('you have requested to see the student name : '+ students[req.params.id]); }) app.listen(3000, function() { console.log('our server is live on posrt 3000'); })
Sunday, February 5, 2017
Wednesday, February 1, 2017
Node.js Tutorial for Beginners 20 - Introduction to Express.js
npm init command
$ npm init This utility will walk you through creating a package.json file. Press ^C at any time to quit. name: (express_test) demo version: (1.0.0) description: Demo of package.json entry point: (index.js) test command: git repository: keywords: author: license: (ISC)
install express via npm
npm install express --save
index.js
var express = require('express'); var app = express(); // GET // POST // PUT // DELETE app.get('/', function(req, rep) { rep.send('this is home page'); }) app.get('/about', function(req, rep) { rep.send('this is about page'); }) app.get('/contect', function(req, rep) { rep.send('this is contect page'); }) app.listen(3000, function() { console.log('our server is live on posrt 3000'); })
package.json
{
"name": "express_test",
"version": "1.0.0",
"description": "",
"main": "index.js",
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1"
},
"author": "",
"license": "ISC",
"dependencies": {
"express": "^4.14.1"
}
}
Friday, January 27, 2017
Thursday, January 19, 2017
Linux Command Line Tutorial For Beginners 37 - netstat command
NETSTAT(8) Linux Programmer's Manual NETSTAT(8) NAME netstat - Print network connections, routing tables, interface statis‐ tics, masquerade connections, and multicast memberships SYNOPSIS netstat [address_family_options] [--tcp|-t] [--udp|-u] [--raw|-w] [--listening|-l] [--all|-a] [--numeric|-n] [--numeric-hosts] [--numeric-ports] [--numeric-users] [--symbolic|-N] [--extend|-e[--extend|-e]] [--timers|-o] [--program|-p] [--verbose|-v] [--continuous|-c] netstat {--route|-r} [address_family_options] [--extend|-e[--extend|-e]] [--verbose|-v] [--numeric|-n] [--numeric-hosts] [--numeric-ports] [--numeric-users] [--continuous|-c] netstat {--interfaces|-i} [--all|-a] [--extend|-e[--extend|-e]] [--ver‐ bose|-v] [--program|-p] [--numeric|-n] [--numeric-hosts] [--numeric- ports] [--numeric-users] [--continuous|-c] netstat {--groups|-g} [--numeric|-n] [--numeric-hosts] [--numeric-ports] [--numeric-users] [--continuous|-c] netstat {--masquerade|-M} [--extend|-e] [--numeric|-n] [--numeric-hosts] [--numeric-ports] [--numeric-users] [--continuous|-c] netstat {--statistics|-s} [--tcp|-t] [--udp|-u] [--raw|-w] netstat {--version|-V} netstat {--help|-h} address_family_options: [-4] [-6] [--protocol={inet,unix,ipx,ax25,netrom,ddp}[,...]] [--unix|-x] [--inet|--ip] [--ax25] [--ipx] [--netrom] [--ddp] DESCRIPTION Netstat prints information about the Linux networking subsystem. The type of information printed is controlled by the first argument, as follows: (none) By default, netstat displays a list of open sockets. If you don't specify any address families, then the active sockets of all configured address families will be printed. --route , -r Display the kernel routing tables. See the description in route(8) for details. netstat -r and route -e produce the same output. --groups , -g Display multicast group membership information for IPv4 and IPv6. --interfaces, -i Display a table of all network interfaces. --masquerade , -M Display a list of masqueraded connections. --statistics , -s Display summary statistics for each protocol. OPTIONS --verbose , -v Tell the user what is going on by being verbose. Especially print some useful information about unconfigured address families. --wide , -W Do not truncate IP addresses by using output as wide as needed. This is optional for now to not break existing scripts. --numeric , -n Show numerical addresses instead of trying to determine symbolic host, port or user names. --numeric-hosts shows numerical host addresses but does not affect the resolution of port or user names. --numeric-ports shows numerical port numbers but does not affect the resolution of host or user names. --numeric-users shows numerical user IDs but does not affect the resolution of host or port names. --protocol=family , -A Specifies the address families (perhaps better described as low level protocols) for which connections are to be shown. family is a comma (',') separated list of address family keywords like inet, unix, ipx, ax25, netrom, and ddp. This has the same effect as using the --inet, --unix (-x), --ipx, --ax25, --netrom, and --ddp options. The address family inet includes raw, udp and tcp protocol sockets. -c, --continuous This will cause netstat to print the selected information every second continuously. -e, --extend Display additional information. Use this option twice for maximum detail. -o, --timers Include information related to networking timers. -p, --program Show the PID and name of the program to which each socket belongs. -l, --listening Show only listening sockets. (These are omitted by default.) -a, --all Show both listening and non-listening sockets. With the --interfaces option, show interfaces that are not up -F Print routing information from the FIB. (This is the default.) -C Print routing information from the route cache. OUTPUT Active Internet connections (TCP, UDP, raw) Proto The protocol (tcp, udp, raw) used by the socket. Recv-Q The count of bytes not copied by the user program connected to this socket. Send-Q The count of bytes not acknowledged by the remote host. Local Address Address and port number of the local end of the socket. Unless the --numeric (-n) option is specified, the socket address is resolved to its canonical host name (FQDN), and the port number is translated into the corresponding service name. Foreign Address Address and port number of the remote end of the socket. Analogous to "Local Address." State The state of the socket. Since there are no states in raw mode and usu‐ ally no states used in UDP, this column may be left blank. Normally this can be one of several values: ESTABLISHED The socket has an established connection. SYN_SENT The socket is actively attempting to establish a connection. SYN_RECV A connection request has been received from the network. FIN_WAIT1 The socket is closed, and the connection is shutting down. FIN_WAIT2 Connection is closed, and the socket is waiting for a shutdown from the remote end. TIME_WAIT The socket is waiting after close to handle packets still in the network. CLOSE The socket is not being used. CLOSE_WAIT The remote end has shut down, waiting for the socket to close. LAST_ACK The remote end has shut down, and the socket is closed. Waiting for acknowledgement. LISTEN The socket is listening for incoming connections. Such sockets are not included in the output unless you specify the --listen‐ ing (-l) or --all (-a) option. CLOSING Both sockets are shut down but we still don't have all our data sent. UNKNOWN The state of the socket is unknown. User The username or the user id (UID) of the owner of the socket. PID/Program name Slash-separated pair of the process id (PID) and process name of the process that owns the socket. --program causes this column to be included. You will also need superuser privileges to see this informa‐ tion on sockets you don't own. This identification information is not yet available for IPX sockets. Timer (this needs to be written) Active UNIX domain Sockets Proto The protocol (usually unix) used by the socket. RefCnt The reference count (i.e. attached processes via this socket). Flags The flags displayed is SO_ACCEPTON (displayed as ACC), SO_WAITDATA (W) or SO_NOSPACE (N). SO_ACCECPTON is used on unconnected sockets if their corresponding processes are waiting for a connect request. The other flags are not of normal interest. Type There are several types of socket access: SOCK_DGRAM The socket is used in Datagram (connectionless) mode. SOCK_STREAM This is a stream (connection) socket. SOCK_RAW The socket is used as a raw socket. SOCK_RDM This one serves reliably-delivered messages. SOCK_SEQPACKET This is a sequential packet socket. SOCK_PACKET Raw interface access socket. UNKNOWN Who ever knows what the future will bring us - just fill in here :-) State This field will contain one of the following Keywords: FREE The socket is not allocated LISTENING The socket is listening for a connection request. Such sockets are only included in the output if you specify the --listening (-l) or --all (-a) option. CONNECTING The socket is about to establish a connection. CONNECTED The socket is connected. DISCONNECTING The socket is disconnecting. (empty) The socket is not connected to another one. UNKNOWN This state should never happen. PID/Program name Process ID (PID) and process name of the process that has the socket open. More info available in Active Internet connections section writ‐ ten above. Path This is the path name as which the corresponding processes attached to the socket. Active IPX sockets (this needs to be done by somebody who knows it) Active NET/ROM sockets (this needs to be done by somebody who knows it) Active AX.25 sockets (this needs to be done by somebody who knows it) NOTES Starting with Linux release 2.2 netstat -i does not show interface sta‐ tistics for alias interfaces. To get per alias interface counters you need to setup explicit rules using the ipchains(8) command. FILES /etc/services -- The services translation file /proc -- Mount point for the proc filesystem, which gives access to kernel status information via the following files. /proc/net/dev -- device information /proc/net/raw -- raw socket information /proc/net/tcp -- TCP socket information /proc/net/udp -- UDP socket information /proc/net/igmp -- IGMP multicast information /proc/net/unix -- Unix domain socket information /proc/net/ipx -- IPX socket information /proc/net/ax25 -- AX25 socket information /proc/net/appletalk -- DDP (appletalk) socket information /proc/net/nr -- NET/ROM socket information /proc/net/route -- IP routing information /proc/net/ax25_route -- AX25 routing information /proc/net/ipx_route -- IPX routing information /proc/net/nr_nodes -- NET/ROM nodelist /proc/net/nr_neigh -- NET/ROM neighbours /proc/net/ip_masquerade -- masqueraded connections /proc/net/snmp -- statistics SEE ALSO route(8), ifconfig(8), ipchains(8), iptables(8), proc(5) BUGS Occasionally strange information may appear if a socket changes as it is viewed. This is unlikely to occur. AUTHORS The netstat user interface was written by Fred Baumgarten <dc6iq@insu1.etec.uni-karlsruhe.de>, the man page basically by Matt Welsh <mdw@tc.cornell.edu>. It was updated by Alan Cox <Alan.Cox@linux.org> but could do with a bit more work. It was updated again by Tuan Hoang <tqhoang@bigfoot.com>. The man page and the command included in the net-tools package is totally rewritten by Bernd Eckenfels <ecki@linux.de>. net-tools 2008-11-16 NETSTAT(8)
Monday, January 16, 2017
Linux Command Line Tutorial For Beginners 37 - grep command
GREP(1) GREP(1) NAME grep, egrep, fgrep, zgrep, zegrep, zfgrep, bzgrep, bzegrep, bzfgrep - print lines matching a pattern SYNOPSIS grep [options] PATTERN [FILE...] grep [options] [-e PATTERN | -f FILE] [FILE...] DESCRIPTION grep searches the named input FILEs (or standard input if no files are named, or the file name - is given) for lines containing a match to the given PATTERN. By default, grep prints the matching lines. In addition, two variant programs egrep and fgrep are available. egrep is the same as grep -E. fgrep is the same as grep -F. zgrep is the same as grep -Z. zegrep is the same as grep -EZ. zfgrep is the same as grep -FZ. OPTIONS -A NUM, --after-context=NUM Print NUM lines of trailing context after matching lines. Places a line containing -- between contiguous groups of matches. -a, --text Process a binary file as if it were text; this is equivalent to the --binary-files=text option. -B NUM, --before-context=NUM Print NUM lines of leading context before matching lines. Places a line containing -- between contiguous groups of matches. -C NUM, --context=NUM Print NUM lines of output context. Places a line containing -- between contiguous groups of matches. -b, --byte-offset Print the byte offset within the input file before each line of output. --binary-files=TYPE If the first few bytes of a file indicate that the file contains binary data, assume that the file is of type TYPE. By default, TYPE is binary, and grep normally outputs either a one-line mes- sage saying that a binary file matches, or no message if there is no match. If TYPE is without-match, grep assumes that a binary file does not match; this is equivalent to the -I option. If TYPE is text, grep processes a binary file as if it were text; this is equivalent to the -a option. Warning: grep --binary-files=text might output binary garbage, which can have nasty side effects if the output is a terminal and if the termi- nal driver interprets some of it as commands. --colour[=WHEN], --color[=WHEN] Surround the matching string with the marker find in GREP_COLOR environment variable. WHEN may be `never', `always', or `auto' -c, --count Suppress normal output; instead print a count of matching lines for each input file. With the -v, --invert-match option (see below), count non-matching lines. -D ACTION, --devices=ACTION If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is read, which means that devices are read just as if they were ordinary files. If ACTION is skip, devices are silently skipped. -d ACTION, --directories=ACTION If an input file is a directory, use ACTION to process it. By default, ACTION is read, which means that directories are read just as if they were ordinary files. If ACTION is skip, direc- tories are silently skipped. If ACTION is recurse, grep reads all files under each directory, recursively; this is equivalent to the -r option. -E, --extended-regexp Interpret PATTERN as an extended regular expression (see below). -e PATTERN, --regexp=PATTERN Use PATTERN as the pattern; useful to protect patterns beginning with -. -F, --fixed-strings Interpret PATTERN as a list of fixed strings, separated by new- lines, any of which is to be matched. -P, --perl-regexp Interpret PATTERN as a Perl regular expression. This option is not supported in FreeBSD. -f FILE, --file=FILE Obtain patterns from FILE, one per line. The empty file con- tains zero patterns, and therefore matches nothing. -G, --basic-regexp Interpret PATTERN as a basic regular expression (see below). This is the default. -H, --with-filename Print the filename for each match. -h, --no-filename Suppress the prefixing of filenames on output when multiple files are searched. --help Output a brief help message. -I Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option. -i, --ignore-case Ignore case distinctions in both the PATTERN and the input files. -L, --files-without-match Suppress normal output; instead print the name of each input file from which no output would normally have been printed. The scanning will stop on the first match. -l, --files-with-matches Suppress normal output; instead print the name of each input file from which output would normally have been printed. The scanning will stop on the first match. -m NUM, --max-count=NUM Stop reading a file after NUM matching lines. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after the last matching line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. When grep stops after NUM matching lines, it outputs any trailing context lines. When the -c or --count option is also used, grep does not output a count greater than NUM. When the -v or --invert-match option is also used, grep stops after outputting NUM non-matching lines. --mmap If possible, use the mmap(2) system call to read input, instead of the default read(2) system call. In some situations, --mmap yields better performance. However, --mmap can cause undefined behavior (including core dumps) if an input file shrinks while grep is operating, or if an I/O error occurs. -n, --line-number Prefix each line of output with the line number within its input file. -o, --only-matching Show only the part of a matching line that matches PATTERN. --label=LABEL Displays input actually coming from standard input as input com- ing from file LABEL. This is especially useful for tools like zgrep, e.g. gzip -cd foo.gz |grep --label=foo something --line-buffered Flush output on every line. Note that this incurs a performance penalty. -q, --quiet, --silent Quiet; do not write anything to standard output. Exit immedi- ately with zero status if any match is found, even if an error was detected. Also see the -s or --no-messages option. -R, -r, --recursive Read all files under each directory, recursively; this is equiv- alent to the -d recurse option. --include=PATTERN Recurse in directories only searching file matching PATTERN. --exclude=PATTERN Recurse in directories skip file matching PATTERN. -s, --no-messages Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep, traditional grep did not con- form to POSIX.2, because traditional grep lacked a -q option and its -s option behaved like GNU grep's -q option. Shell scripts intended to be portable to traditional grep should avoid both -q and -s and should redirect output to /dev/null instead. -U, --binary Treat the file(s) as binary. By default, under MS-DOS and MS- Windows, grep guesses the file type by looking at the contents of the first 32KB read from the file. If grep decides the file is a text file, it strips the CR characters from the original file contents (to make regular expressions with ^ and $ work correctly). Specifying -U overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with CR/LF pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Win- dows. -u, --unix-byte-offsets Report Unix-style byte offsets. This switch causes grep to report byte offsets as if the file were Unix-style text file, i.e. with CR characters stripped off. This will produce results identical to running grep on a Unix machine. This option has no effect unless -b option is also used; it has no effect on plat- forms other than MS-DOS and MS-Windows. -V, --version Print the version number of grep to standard error. This ver- sion number should be included in all bug reports (see below). -v, --invert-match Invert the sense of matching, to select non-matching lines. -w, --word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word con- stituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word- constituent characters are letters, digits, and the underscore. -x, --line-regexp Select only those matches that exactly match the whole line. -y Obsolete synonym for -i. --null Output a zero byte (the ASCII NUL character) instead of the character that normally follows a file name. For example, grep -l --null outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like find -print0, perl -0, sort -z, and xargs -0 to process arbitrary file names, even those that contain newline characters. -Z, --decompress Decompress the input data before searching. This option is only available if compiled with zlib(3) library. -J, --bz2decompress Decompress the bzip2(1) compressed input data before searching. REGULAR EXPRESSIONS A regular expression is a pattern that describes a set of strings. Regular expressions are constructed analogously to arithmetic expres- sions, by using various operators to combine smaller expressions. grep understands two different versions of regular expression syntax: "basic" and "extended." In GNU grep, there is no difference in avail- able functionality using either syntax. In other implementations, basic regular expressions are less powerful. The following description applies to extended regular expressions; differences for basic regular expressions are summarized afterwards. The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any metacharacter with special meaning may be quoted by preceding it with a backslash. A bracket expression is a list of characters enclosed by [ and ]. It matches any single character in that list; if the first character of the list is the caret ^ then it matches any character not in the list. For example, the regular expression [0123456789] matches any single digit. Within a bracket expression, a range expression consists of two charac- ters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictio- nary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C. Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:blank:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means [0-9A-Za-z], except the latter form depends upon the C locale and the ASCII character encoding, whereas the former is independent of locale and character set. (Note that the brackets in these class names are part of the symbolic names, and must be included in addition to the brackets delimiting the bracket list.) Most metacharacters lose their special meaning inside lists. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last. The period . matches any single character. The symbol \w is a synonym for [[:alnum:]] and \W is a synonym for [^[:alnum:]]. The caret ^ and the dollar sign $ are metacharacters that respectively match the empty string at the beginning and end of a line. The symbols \< and \> respectively match the empty string at the beginning and end of a word. The symbol \b matches the empty string at the edge of a word, and \B matches the empty string provided it's not at the edge of a word. A regular expression may be followed by one of several repetition oper- ators: ? The preceding item is optional and matched at most once. * The preceding item will be matched zero or more times. + The preceding item will be matched one or more times. {n} The preceding item is matched exactly n times. {n,} The preceding item is matched n or more times. {n,m} The preceding item is matched at least n times, but not more than m times. Two regular expressions may be concatenated; the resulting regular expression matches any string formed by concatenating two substrings that respectively match the concatenated subexpressions. Two regular expressions may be joined by the infix operator |; the resulting regular expression matches any string matching either subex- pression. Repetition takes precedence over concatenation, which in turn takes precedence over alternation. A whole subexpression may be enclosed in parentheses to override these precedence rules. The backreference \n, where n is a single digit, matches the substring previously matched by the nth parenthesized subexpression of the regu- lar expression. In basic regular expressions the metacharacters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \). Traditional egrep did not support the { metacharacter, and some egrep implementations support \{ instead, so portable scripts should avoid { in egrep patterns and should use [{] to match a literal {. GNU egrep attempts to support traditional usage by assuming that { is not special if it would be the start of an invalid interval specifica- tion. For example, the shell command egrep '{1' searches for the two- character string {1 instead of reporting a syntax error in the regular expression. POSIX.2 allows this behavior as an extension, but portable scripts should avoid it. ENVIRONMENT VARIABLES Grep's behavior is affected by the following environment variables. A locale LC_foo is specified by examining the three environment vari- ables LC_ALL, LC_foo, LANG, in that order. The first of these vari- ables that is set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set to pt_BR, then Brazilian Portuguese is used for the LC_MESSAGES locale. The C locale is used if none of these environment variables are set, or if the locale catalog is not installed, or if grep was not compiled with national language support (NLS). GREP_OPTIONS This variable specifies default options to be placed in front of any explicit options. For example, if GREP_OPTIONS is '--binary-files=without-match --directories=skip', grep behaves as if the two options --binary-files=without-match and --direc- tories=skip had been specified before any explicit options. Option specifications are separated by whitespace. A backslash escapes the next character, so it can be used to specify an option containing whitespace or a backslash. GREP_COLOR Specifies the marker for highlighting. LC_ALL, LC_COLLATE, LANG These variables specify the LC_COLLATE locale, which determines the collating sequence used to interpret range expressions like [a-z]. LC_ALL, LC_CTYPE, LANG These variables specify the LC_CTYPE locale, which determines the type of characters, e.g., which characters are whitespace. LC_ALL, LC_MESSAGES, LANG These variables specify the LC_MESSAGES locale, which determines the language that grep uses for messages. The default C locale uses American English messages. POSIXLY_CORRECT If set, grep behaves as POSIX.2 requires; otherwise, grep behaves more like other GNU programs. POSIX.2 requires that options that follow file names must be treated as file names; by default, such options are permuted to the front of the operand list and are treated as options. Also, POSIX.2 requires that unrecognized options be diagnosed as "illegal", but since they are not really against the law the default is to diagnose them as "invalid". DIAGNOSTICS Normally, exit status is 0 if selected lines are found and 1 otherwise. But the exit status is 2 if an error occurred, unless the -q or --quiet or --silent option is used and a selected line is found. BUGS Email bug reports to bug-gnu-utils@gnu.org. Be sure to include the word "grep" somewhere in the "Subject:" field. Large repetition counts in the {n,m} construct may cause grep to use lots of memory. In addition, certain other obscure regular expressions require exponential time and space, and may cause grep to run out of memory. Backreferences are very slow, and may require exponential time. GNU Project 2002/01/22 GREP(1)
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