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Aliases allow a string to be substituted for a word when it is used as the first word of a simple command. The shell maintains a list of aliases that may be set and unset with the alias and unalias builtin commands. You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects. bg [jobspec …] Resume each suspended job jobspec in the background, as if it had been started with ‘&’. If jobspec is not supplied, the current job is used. The return status is zero unless it is run when job control is not enabled, or, when run with job control enabled, any jobspec was not found or specifies a job that was started without job control. There may be an arbitrary number of case clauses, each terminated by a ‘;;’, ‘;&’, or ‘;;&’. The first pattern that matches determines the command-list that is executed. It’s a common idiom to use ‘*’ as the final pattern to define the default case, since that pattern will always match. For example, in the default C locale, ‘[a-dx-z]’ is equivalent to ‘[abcdxyz]’. Many locales sort characters in dictionary order, and in these locales ‘[a-dx-z]’ is typically not equivalent to ‘[abcdxyz]’; it might be equivalent to ‘[aBbCcDdxXyYz]’, for example. To obtain the traditional interpretation of ranges in bracket expressions, you can force the use of the C locale by setting the LC_COLLATE or LC_ALL environment variable to the value ‘C’, or enable the globasciiranges shell option.

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The optional p is a digit specifying the precision, the number of fractional digits after a decimal point. A value of 0 causes no decimal point or fraction to be output. At most three places after the decimal point may be specified; values of p greater than 3 are changed to 3. If p is not specified, the value 3 is used. Re-execute the last keyboard macro defined, by making the characters in the macro appear as if typed at the keyboard. Do not use the GNU Readline library (see Command Line Editing) to read command lines when the shell is interactive. If parameter is unset or null, the expansion of word is assigned to parameter. The value of parameter is then substituted. Positional parameters and special parameters may not be assigned to in this way.

If a word begins with an unquoted tilde character (‘~’), all of the characters up to the first unquoted slash (or all characters, if there is no unquoted slash) are considered a tilde-prefix. If none of the characters in the tilde-prefix are quoted, the characters in the tilde-prefix following the tilde are treated as a possible name. If this name is the null string, the tilde is replaced with the value of the HOME shell variable. If HOME is unset, the home directory of the user executing the shell is substituted instead. Otherwise, the tilde-prefix is replaced with the home directory associated with the specified name. There is other POSIX behavior that Bash does not implement by default even when in POSIX mode. Specifically:

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Substring indexing is zero-based unless the positional parameters are used, in which case the indexing starts at 1 by default. If offset is 0, and the positional parameters are used, $@ is prefixed to the list. The word before point is treated as a pattern for pathname expansion, with an asterisk implicitly appended. This pattern is used to generate a list of matching file names for possible completions. Bash contains features that appear in other popular shells, and some features that only appear in Bash. Some of the shells that Bash has borrowed concepts from are the Bourne Shell (sh), the Korn Shell (ksh), and the C-shell (csh and its successor, tcsh). The following menu breaks the features up into categories, noting which features were inspired by other shells and which are specific to Bash.

Bash (Unix shell) - Wikipedi

Complicated extended pattern matching against long strings is slow, especially when the patterns contain alternations and the strings contain multiple matches. Using separate matches against shorter strings, or using arrays of strings instead of a single long string, may be faster. From the left side pane, choose “For developers.” You’ll see an option for “Developer mode.” Enable it.If the -e option is supplied with -P and the current working directory cannot be successfully determined after a successful directory change, cd will return an unsuccessful status.

bash$ echo a{d,c,b}e ade ace abe A sequence expression takes the form {x..y[..incr]}, where x and y are either integers or single characters, and incr, an optional increment, is an integer. When integers are supplied, the expression expands to each number between x and y, inclusive. Supplied integers may be prefixed with ‘0’ to force each term to have the same width. When either x or y begins with a zero, the shell attempts to force all generated terms to contain the same number of digits, zero-padding where necessary. When characters are supplied, the expression expands to each character lexicographically between x and y, inclusive, using the default C locale. Note that both x and y must be of the same type. When the increment is supplied, it is used as the difference between each term. The default increment is 1 or -1 as appropriate. Once you know the name of the command, simply place on a line in the init file the name of the key you wish to bind the command to, a colon, and then the name of the command. There can be no space between the key name and the colon – that will be interpreted as part of the key name. The name of the key can be expressed in different ways, depending on what you find most comfortable. When the shell is waiting for a job or process using the wait builtin, and job control is enabled, wait will return when the job changes state. The -f option will force wait to wait until the job or process terminates before returning. There could be several processes representing the same program running in memory at the same time. For example I could have two terminals open and be running the command cp in both of them. In this case there would be two cp processes currently existing on the system. Once they are finished running the system then destroys them and there are no longer any processes representing the program cp.Capitalize the current (or following) word. With a negative argument, capitalize the previous word, but do not move the cursor.

This section describes builtin commands which are unique to or have been extended in Bash. Some of these commands are specified in the POSIX standard. If set, Bash changes its behavior to that of version 3.1 with respect to quoted arguments to the conditional command’s ‘=~’ operator and with respect to locale-specific string comparison when using the [[ conditional command’s ‘<’ and ‘>’ operators. Bash versions prior to bash-4.1 use ASCII collation and strcmp(3); bash-4.1 and later use the current locale’s collation sequence and strcoll(3).

How to Install and Use the Linux Bash Shell on Windows 1

  1. This section describes Readline commands that may be bound to key sequences. You can list your key bindings by executing bind -P or, for a more terse format, suitable for an inputrc file, bind -p. (See Bash Builtins.) Command names without an accompanying key sequence are unbound by default.
  2. Readline provides commands for searching through the command history (see Bash History Facilities) for lines containing a specified string. There are two search modes: incremental and non-incremental.
  3. e the column length for printing selection lists. Automatically set if the checkwinsize option is enabled (see The Shopt Builtin), or in an interactive shell upon receipt of a SIGWINCH.
  4. If multiple options are supplied, the -D option takes precedence over -E, and both take precedence over -I
  5. If the first argument is ‘!’, the expression is true if and only if the second argument is null. If the first argument is one of the unary conditional operators (see Bash Conditional Expressions), the expression is true if the unary test is true. If the first argument is not a valid unary operator, the expression is false.

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Job control refers to the ability to selectively stop (suspend) the execution of processes and continue (resume) their execution at a later point. A user typically employs this facility via an interactive interface supplied jointly by the operating system kernel’s terminal driver and Bash. parallel "zcat {} | bzip2 >{.}.bz2 && rm {}" ::: *.gz If a command generates output, you may want to preserve the input order in the output. For instance, the following command You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

The term= form may be used to include terminal-specific key bindings, perhaps to bind the key sequences output by the terminal’s function keys. The word on the right side of the ‘=’ is tested against both the full name of the terminal and the portion of the terminal name before the first ‘-’. This allows sun to match both sun and sun-cmd, for instance. The $if construct allows bindings to be made based on the editing mode, the terminal being used, or the application using Readline. The text of the test, after any comparison operator, extends to the end of the line; unless otherwise noted, no characters are required to isolate it. Controls the action of the shell on receipt of an EOF character as the sole input. If set, the value denotes the number of consecutive EOF characters that can be read as the first character on an input line before the shell will exit. If the variable exists but does not have a numeric value, or has no value, then the default is 10. If the variable does not exist, then EOF signifies the end of input to the shell. This is only in effect for interactive shells.

unalias [-a] [name … ] Remove each name from the list of aliases. If -a is supplied, all aliases are removed. Aliases are described in Aliases. pattern='[[:space:]]*?(a)b' [[ $line =~ $pattern ]] If you want to match a character that’s special to the regular expression grammar, it has to be quoted to remove its special meaning. This means that in the pattern ‘xxx.txt’, the ‘.’ matches any character in the string (its usual regular expression meaning), but in the pattern ‘"xxx.txt"’ it can only match a literal ‘.’. Shell programmers should take special care with backslashes, since backslashes are used both by the shell and regular expressions to remove the special meaning from the following character. The following two sets of commands are not equivalent: This enables support for multibyte characters if the operating system provides the necessary support.

If you’re not sure which Linux environment to install, we recommend Ubuntu. This popular Linux distribution was previously the only option available, but other Linux systems are now available for people who have more specific needs.After these expansions are performed, quote characters present in the original word are removed unless they have been quoted themselves (quote removal). Notice how C-f moves forward a character, while M-f moves forward a word. It is a loose convention that control keystrokes operate on characters while meta keystrokes operate on words. As noted above, if a non-interactive shell is invoked with the -- option, Bash attempts to read and execute commands from the shell startup files.

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When set to ‘on’, Readline will try to enable any meta modifier key the terminal claims to support when it is called. On many terminals, the meta key is used to send eight-bit characters. The default is ‘on’. The expansion is a string that is the result of expanding the value of parameter as if it were a prompt string (see Controlling the Prompt). When -p is supplied without name arguments, declare will display the attributes and values of all variables having the attributes specified by the additional options. If no other options are supplied with -p, declare will display the attributes and values of all shell variables. The -f option will restrict the display to shell functions.

coproc [NAME] command [redirections] This creates a coprocess named NAME. If NAME is not supplied, the default name is COPROC. NAME must not be supplied if command is a simple command (see Simple Commands); otherwise, it is interpreted as the first word of the simple command. How often (in seconds) that the shell should check for mail in the files specified in the MAILPATH or MAIL variables. The default is 60 seconds. When it is time to check for mail, the shell does so before displaying the primary prompt. If this variable is unset, or set to a value that is not a number greater than or equal to zero, the shell disables mail checking. help [-dms] [pattern] Display helpful information about builtin commands. If pattern is specified, help gives detailed help on all commands matching pattern, otherwise a list of the builtins is printed.

If a command fails because of an error during expansion or redirection, the exit status is greater than zero. The value of this variable is used as the prompt for the select command. If this variable is not set, the select command prompts with ‘#? ’

If Bash is waiting for a command to complete and receives a signal for which a trap has been set, the trap will not be executed until the command completes. When Bash is waiting for an asynchronous command via the wait builtin, the reception of a signal for which a trap has been set will cause the wait builtin to return immediately with an exit status greater than 128, immediately after which the trap is executed. The rules concerning the definition and use of aliases are somewhat confusing. Bash always reads at least one complete line of input, and all lines that make up a compound command, before executing any of the commands on that line or the compound command. Aliases are expanded when a command is read, not when it is executed. Therefore, an alias definition appearing on the same line as another command does not take effect until the next line of input is read. The commands following the alias definition on that line are not affected by the new alias. This behavior is also an issue when functions are executed. Aliases are expanded when a function definition is read, not when the function is executed, because a function definition is itself a command. As a consequence, aliases defined in a function are not available until after that function is executed. To be safe, always put alias definitions on a separate line, and do not use alias in compound commands.

If you have to use a make that does not supports the VPATH variable, you can compile Bash for one architecture at a time in the source code directory. After you have installed Bash for one architecture, use ‘make distclean’ before reconfiguring for another architecture. Produces a listing using full pathnames; the default listing format uses a tilde to denote the home directory. Any completions specified by a filename expansion pattern to the -G option are generated next. The words generated by the pattern need not match the word being completed. The GLOBIGNORE shell variable is not used to filter the matches, but the FIGNORE shell variable is used.

In func2, var = func1 local func1() { local var='func1 local' func2 } func2() { echo "In func2, var = $var" } var=global func1 The unset builtin also acts using the same dynamic scope: if a variable is local to the current scope, unset will unset it; otherwise the unset will refer to the variable found in any calling scope as described above. If a variable at the current local scope is unset, it will remain so until it is reset in that scope or until the function returns. Once the function returns, any instance of the variable at a previous scope will become visible. If the unset acts on a variable at a previous scope, any instance of a variable with that name that had been shadowed will become visible. HISTIGNORE subsumes the function of HISTCONTROL. A pattern of ‘&’ is identical to ignoredups, and a pattern of ‘[ ]*’ is identical to ignorespace. Combining these two patterns, separating them with a colon, provides the functionality of ignoreboth. A colon-separated list of suffixes to ignore when performing filename completion. A filename whose suffix matches one of the entries in FIGNORE is excluded from the list of matched filenames. A sample value is ‘.o:~’

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Bash

  1. Enable ‘!’ style history substitution (see History Interaction). This option is on by default for interactive shells.
  2. Expressions may be combined using the following operators, listed in decreasing order of precedence:
  3. If set to ‘on’, Readline uses an internal more-like pager to display a screenful of possible completions at a time. This variable is ‘on’ by default.
  4. The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.
  5. Contains the name of a file in the same format as /etc/hosts that should be read when the shell needs to complete a hostname. The list of possible hostname completions may be changed while the shell is running; the next time hostname completion is attempted after the value is changed, Bash adds the contents of the new file to the existing list. If HOSTFILE is set, but has no value, or does not name a readable file, Bash attempts to read /etc/hosts to obtain the list of possible hostname completions. When HOSTFILE is unset, the hostname list is cleared.
  6. The wordlist is split using the characters in the IFS special variable as delimiters, and each resultant word is expanded. The possible completions are the members of the resultant list which match the word being completed.

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The most common way to obtain additional completion functionality beyond the default actions complete and compgen provide is to use a shell function and bind it to a particular command using complete -F. Next, the string specified as the argument to the -W option is considered. The string is first split using the characters in the IFS special variable as delimiters. Shell quoting is honored within the string, in order to provide a mechanism for the words to contain shell metacharacters or characters in the value of IFS. Each word is then expanded using brace expansion, tilde expansion, parameter and variable expansion, command substitution, and arithmetic expansion, as described above (see Shell Expansions). The results are split using the rules described above (see Word Splitting). The results of the expansion are prefix-matched against the word being completed, and the matching words become the possible completions. [[ expression ]] Return a status of 0 or 1 depending on the evaluation of the conditional expression expression. Expressions are composed of the primaries described below in Bash Conditional Expressions. Word splitting and filename expansion are not performed on the words between the [[ and ]]; tilde expansion, parameter and variable expansion, arithmetic expansion, command substitution, process substitution, and quote removal are performed. Conditional operators such as ‘-f’ must be unquoted to be recognized as primaries.

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What is a Bash Script? - Bash Scripting Tutoria

  1. Without a numeric argument, the value of the comment-begin variable is inserted at the beginning of the current line. If a numeric argument is supplied, this command acts as a toggle: if the characters at the beginning of the line do not match the value of comment-begin, the value is inserted, otherwise the characters in comment-begin are deleted from the beginning of the line. In either case, the line is accepted as if a newline had been typed. The default value of comment-begin causes this command to make the current line a shell comment. If a numeric argument causes the comment character to be removed, the line will be executed by the shell.
  2. Attempt to move point to the same physical screen column on the previous physical screen line. This will not have the desired effect if the current Readline line does not take up more than one physical line or if point is not greater than the length of the prompt plus the screen width.
  3. Other options, if specified, have the following meanings. The arguments to the -G, -W, and -X options (and, if necessary, the -P and -S options) should be quoted to protect them from expansion before the complete builtin is invoked.
  4. $ a=foo $ [ "$a" = foo ]; echo "$?" # POSIX sh 0 $ [ "$a" == foo ]; echo "$?" # bash specific 0 $ [ "$a" -eq foo ]; echo "$?" # wrong -bash: [: foo: integer expression expected 2 (Side note: Quote those variable expansions! Do not leave out the double quotes above.)
  5. Tell Readline not to quote the completed words if they are filenames (quoting filenames is the default).
  6. g from a ter
  7. alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit A character class matches any character belonging to that class. The word character class matches letters, digits, and the character ‘_’.

Search forward starting at the current line and moving ‘down’ through the history as necessary. This is an incremental search. Set the default value of the globasciiranges shell option described above under The Shopt Builtin to be enabled. This controls the behavior of character ranges when used in pattern matching bracket expressions. An array variable consisting of the individual words in the current command line. The line is split into words as Readline would split it, using COMP_WORDBREAKS as described above. This variable is available only in shell functions invoked by the programmable completion facilities (see Programmable Completion). If this variable is in the environment when Bash starts, the shell enters POSIX mode (see Bash POSIX Mode) before reading the startup files, as if the --posix invocation option had been supplied. If it is set while the shell is running, Bash enables POSIX mode, as if the command If a word designator is supplied without an event specification, the previous command is used as the event.

Bash Equality Operators ( == , -eq ) - Stack Overflo

Assuming you have 64-bit Windows, to get started, head to Control Panel > Programs > Turn Windows Features On Or Off. Enable the “Windows Subsystem for Linux” option in the list, and then click the “OK” button.When a program is invoked it is given an array of strings called the environment. This is a list of name-value pairs, of the form name=value. Move back to the start of the current or previous word. Words are delimited by non-quoted shell metacharacters. In an interactive shell, the value is interpreted as the number of seconds to wait for a line of input after issuing the primary prompt. Bash terminates after waiting for that number of seconds if a complete line of input does not arrive. Non-incremental searches read the entire search string before starting to search for matching history lines. The search string may be typed by the user or be part of the contents of the current line.

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Before a command is executed, its input and output may be redirected using a special notation interpreted by the shell. Redirection allows commands’ file handles to be duplicated, opened, closed, made to refer to different files, and can change the files the command reads from and writes to. Redirection may also be used to modify file handles in the current shell execution environment. The following redirection operators may precede or appear anywhere within a simple command or may follow a command. Redirections are processed in the order they appear, from left to right. When you use a kill command, the text is saved in a kill-ring. Any number of consecutive kills save all of the killed text together, so that when you yank it back, you get it all. The kill ring is not line specific; the text that you killed on a previously typed line is available to be yanked back later, when you are typing another line.

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If no arguments follow this option, then the positional parameters are unset. Otherwise, the positional parameters are set to the arguments, even if some of them begin with a ‘-’. This variable expands to the number of seconds since the shell was started. Assignment to this variable resets the count to the value assigned, and the expanded value becomes the value assigned plus the number of seconds since the assignment. This variable, when set to ‘on’, causes Readline to display an asterisk (‘*’) at the start of history lines which have been modified. This variable is ‘off’ by default.

Bash - definition of bash by The Free Dictionar

command1 || command2 command2 is executed if, and only if, command1 returns a non-zero exit status. The remaining N arguments are positional parameters and are assigned, in order, to $1, $2, … $N. The special parameter # is set to N. This will run as many mv commands as there are files in the current directory. You can emulate a parallel xargs by adding the -X option:

Bash Definition of Bash at Dictionary

  1. echo {A,B}.js {A,B} Same as A B {A,B}.js Same as A.js B.js {1..5} Same as 1 2 3 4 5 See: Brace expansion
  2. This chapter provides basic instructions for installing Bash on the various supported platforms. The distribution supports the GNU operating systems, nearly every version of Unix, and several non-Unix systems such as BeOS and Interix. Other independent ports exist for MS-DOS, OS/2, and Windows platforms.
  3. Next: Arithmetic Expansion, Previous: Shell Parameter Expansion, Up: Shell Expansions   [Contents][Index]

Lowercase the current (or following) word. With a negative argument, lowercase the previous word, but do not move the cursor. Next: Commands For Killing, Previous: Commands For History, Up: Bindable Readline Commands   [Contents][Index]The exit status is used by the Bash conditional commands (see Conditional Constructs) and some of the list constructs (see Lists). Use the curses library instead of the termcap library. This should be supplied if your system has an inadequate or incomplete termcap database.

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Bash is an acronym for ‘Bourne-Again SHell’. The Bourne shell is the traditional Unix shell originally written by Stephen Bourne. All of the Bourne shell builtin commands are available in Bash, The rules for evaluation and quoting are taken from the POSIX specification for the ‘standard’ Unix shell. An array variable whose members are the line numbers in source files where each corresponding member of FUNCNAME was invoked. ${BASH_LINENO[$i]} is the line number in the source file (${BASH_SOURCE[$i+1]}) where ${FUNCNAME[$i]} was called (or ${BASH_LINENO[$i-1]} if referenced within another shell function). Use LINENO to obtain the current line number. Process substitution allows a process’s input or output to be referred to using a filename. It takes the form of Bash and Bash scripts 1.1. Common shell programs 1.2. Advantages of the Bourne Again SHell 1.3. Executing commands 1.4. Building blocks 1.5. Developing good scripts 1.6. Summary 1.7. Exercises 2. Writing and debugging scripts 2.1. Creating and running a script 2.2. Script basics 2.3. Debugging Bash scripts 2.4. Summary 2.5. Exercises 3. The. The WSL optional component is not enabled. Please enable it and try again. See https://aka.ms/wslinstall for details. Error: 0x8007007e Press any key to continue...And when you press any key, the application closes immediately.

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Matches any one of the enclosed characters. A pair of characters separated by a hyphen denotes a range expression; any character that falls between those two characters, inclusive, using the current locale’s collating sequence and character set, is matched. If the first character following the ‘[’ is a ‘!’ or a ‘^’ then any character not enclosed is matched. A ‘-’ may be matched by including it as the first or last character in the set. A ‘]’ may be matched by including it as the first character in the set. The sorting order of characters in range expressions is determined by the current locale and the values of the LC_COLLATE and LC_ALL shell variables, if set. The $PATH variable is an individual user variable so each user on a system may set it to suit themselves.Once installed using complete, _comp_cd will be called every time we attempt word completion for a cd command. If set, do not resolve symbolic links when performing commands such as cd which change the current directory. The physical directory is used instead. By default, Bash follows the logical chain of directories when performing commands which change the current directory.

Next: Commands For Text, Previous: Commands For Moving, Up: Bindable Readline Commands   [Contents][Index]If there is a command name left after expansion, execution proceeds as described below. Otherwise, the command exits. If one of the expansions contained a command substitution, the exit status of the command is the exit status of the last command substitution performed. If there were no command substitutions, the command exits with a status of zero. The function relies on the complete and compgen builtins to do much of the work, adding only the things that the Bash cd does beyond accepting basic directory names: tilde expansion (see Tilde Expansion), searching directories in $CDPATH, which is described above (see Bourne Shell Builtins), and basic support for the cdable_vars shell option (see The Shopt Builtin). _comp_cd modifies the value of IFS so that it contains only a newline to accommodate file names containing spaces and tabs – compgen prints the possible completions it generates one per line. The current working directory, with $HOME abbreviated with a tilde (uses the $PROMPT_DIRTRIM variable).

An event designator is a reference to a command line entry in the history list. Unless the reference is absolute, events are relative to the current position in the history list. If set to ‘on’, Readline will undo all changes to history lines before returning when accept-line is executed. By default, history lines may be modified and retain individual undo lists across calls to readline. The default is ‘off’. parallel -j 10 < file will evaluate the commands using the shell (since no explicit command is supplied as an argument), in blocks of ten shell jobs at a time. If set to a numeric value greater than 0, defines a maximum function nesting level. Function invocations that exceed this nesting level will cause the current command to abort. Displays the Nth directory (counting from the right of the list printed by dirs when invoked without options), starting with zero.

Commands And Arguments - Bash

Use keymap as the keymap to be affected by the subsequent bindings. Acceptable keymap names are emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi-move, vi-command, and vi-insert. vi is equivalent to vi-command (vi-move is also a synonym); emacs is equivalent to emacs-standard. $ [[ "yes" -eq "no" ]]; echo $? 0 The reason is that Bash is untyped. The -eq causes the strings to be interpreted as integers if possible including base conversion:To open the Linux environment you installed, just open the Start menu and search for whatever distribution you installed. For example, if you installed Ubuntu, launch the Ubuntu shortcut.

Redirections (Bash Reference Manual

If Bash finds this variable in the environment when the shell starts with value ‘t’, it assumes that the shell is running in an Emacs shell buffer and disables line editing. When the shell is in POSIX mode (see Bash POSIX Mode), time may be followed by a newline. In this case, the shell displays the total user and system time consumed by the shell and its children. The TIMEFORMAT variable may be used to specify the format of the time information. The text M-k is read as ‘Meta-K’ and describes the character produced when the Meta key (if you have one) is depressed, and the k key is pressed. The Meta key is labeled ALT on many keyboards. On keyboards with two keys labeled ALT (usually to either side of the space bar), the ALT on the left side is generally set to work as a Meta key. The ALT key on the right may also be configured to work as a Meta key or may be configured as some other modifier, such as a Compose key for typing accented characters. The comp-option controls several aspects of the compspec’s behavior beyond the simple generation of completions. comp-option may be one of:

Drag the word before point past the word after point, moving point past that word as well. If the insertion point is at the end of the line, this transposes the last two words on the line. The version test may be used to perform comparisons against specific Readline versions. The version expands to the current Readline version. The set of comparison operators includes ‘=’ (and ‘==’), ‘!=’, ‘<=’, ‘>=’, ‘<’, and ‘>’. The version number supplied on the right side of the operator consists of a major version number, an optional decimal point, and an optional minor version (e.g., ‘7.1’). If the minor version is omitted, it is assumed to be ‘0’. The operator may be separated from the string version and from the version number argument by whitespace. The following example sets a variable if the Readline version being used is 7.0 or newer: The Windows Subsystem for Linux, introduced in the Anniversary Update, became a stable feature in the Fall Creators Update. You can now run Ubuntu and openSUSE on Windows, with Fedora and more Linux distributions coming soon.The optional l specifies a longer format, including minutes, of the form MMmSS.FFs. The value of p determines whether or not the fraction is included.

This chapter describes the shell variables that Bash uses. Bash automatically assigns default values to a number of variables. continue [n] Resume the next iteration of an enclosing for, while, until, or select loop. If n is supplied, the execution of the nth enclosing loop is resumed. n must be greater than or equal to 1. The return status is zero unless n is not greater than or equal to 1. The -p option will display the attributes and values of each name. When -p is used with name arguments, additional options, other than -f and -F, are ignored.

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If you need to do unusual things to compile Bash, please try to figure out how configure could check whether or not to do them, and mail diffs or instructions to bash-maintainers@gnu.org so they can be considered for the next release. let expression [expression …] The let builtin allows arithmetic to be performed on shell variables. Each expression is evaluated according to the rules given below in Shell Arithmetic. If the last expression evaluates to 0, let returns 1; otherwise 0 is returned. Looking for online definition of BASH or what BASH stands for? BASH is listed in the World's largest and most authoritative dictionary database of abbreviations and acronyms The Free Dictionar If set, and programmable completion is enabled, Bash treats a command name that doesn’t have any completions as a possible alias and attempts alias expansion. If it has an alias, Bash attempts programmable completion using the command word resulting from the expanded alias. Enclosing characters in single quotes (‘'’) preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash.

If Statements - Bash Scripting Tutoria

In addition to the creation of a subshell, there is a subtle difference between these two constructs due to historical reasons. The braces are reserved words, so they must be separated from the list by blanks or other shell metacharacters. The parentheses are operators, and are recognized as separate tokens by the shell even if they are not separated from the list by whitespace. Swap the point with the mark. The current cursor position is set to the saved position, and the old cursor position is saved as the mark. Job control is enabled (see Job Control). All processes run in a separate process group. When a background job completes, the shell prints a line containing its exit status. There are several single-character options that may be supplied at invocation which are not available with the set builtin. find . -depth 1 \! -name '.*' -print0 | parallel -0 -X mv {} destdir GNU Parallel can replace certain common idioms that operate on lines read from a file (in this case, filenames listed one per line):

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If the tilde-prefix is ‘~+’, the value of the shell variable PWD replaces the tilde-prefix. If the tilde-prefix is ‘~-’, the value of the shell variable OLDPWD, if it is set, is substituted. [[ $line =~ [[:space:]]*?(a)b ]] That means values like ‘aab’ and ‘ aaaaaab’ will match, as will a line containing a ‘b’ anywhere in its value. In addition, several keys have their own names. Specifically, DEL, ESC, LFD, SPC, RET, and TAB all stand for themselves when seen in this text, or in an init file (see Readline Init File). If your keyboard lacks a LFD key, typing C-j will produce the desired character. The RET key may be labeled Return or Enter on some keyboards.

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Go to Settings -> Storage -> More Storage Settings: Change where new content is saved and select C Drive here.command [-pVv] command [arguments …] Runs command with arguments ignoring any shell function named command. Only shell builtin commands or commands found by searching the PATH are executed. If there is a shell function named ls, running ‘command ls’ within the function will execute the external command ls instead of calling the function recursively. The -p option means to use a default value for PATH that is guaranteed to find all of the standard utilities. The return status in this case is 127 if command cannot be found or an error occurred, and the exit status of command otherwise.

trap [-lp] [arg] [sigspec …] The commands in arg are to be read and executed when the shell receives signal sigspec. If arg is absent (and there is a single sigspec) or equal to ‘-’, each specified signal’s disposition is reset to the value it had when the shell was started. If arg is the null string, then the signal specified by each sigspec is ignored by the shell and commands it invokes. If arg is not present and -p has been supplied, the shell displays the trap commands associated with each sigspec. If no arguments are supplied, or only -p is given, trap prints the list of commands associated with each signal number in a form that may be reused as shell input. The -l option causes the shell to print a list of signal names and their corresponding numbers. Each sigspec is either a signal name or a signal number. Signal names are case insensitive and the SIG prefix is optional. Just search for the Linux distribution you installed in the previous step. In my case it was Ubuntu. You’ll see that it runs like a normal Windows application.Boolean variables (those that can be set to on or off) are set to on if the value is null or empty, on (case-insensitive), or 1. Any other value results in the variable being set to off.

exit [n] Exit the shell, returning a status of n to the shell’s parent. If n is omitted, the exit status is that of the last command executed. Any trap on EXIT is executed before the shell terminates. $ [[ 10 -lt 2 ]]; echo $? 1 In comments, there is a question of the technical reason using the integer -eq on strings returns True for strings that are not the same:If set, Bash replaces directory names with the results of word expansion when performing filename completion. This changes the contents of the readline editing buffer. If not set, Bash attempts to preserve what the user typed. The command number and the history number are usually different: the history number of a command is its position in the history list, which may include commands restored from the history file (see Bash History Facilities), while the command number is the position in the sequence of commands executed during the current shell session. You’ll see a list of every Linux distribution currently available in the Windows Store. As of the Fall Creators Update, this includes Ubuntu, openSUSE Leap, and openSUSE Enterprise, with a promise that Fedora will arrive soon.

If the -t option is used, type prints a single word which is one of ‘alias’, ‘function’, ‘builtin’, ‘file’ or ‘keyword’, if name is an alias, shell function, shell builtin, disk file, or shell reserved word, respectively. If the name is not found, then nothing is printed, and type returns a failure status. The maximum number of commands to remember on the history list. If the value is 0, commands are not saved in the history list. Numeric values less than zero result in every command being saved on the history list (there is no limit). The shell sets the default value to 500 after reading any startup files.

Use and save the results of the tests in file instead of ./config.cache. Set file to /dev/null to disable caching, for debugging configure. Once a compspec has been found, it is used to generate the list of matching words. If a compspec is not found, the default Bash completion described above (see Commands For Completion) is performed. 爱词霸权威在线词典,为您提供bash的中文意思,bash的用法讲解,bash的读音,bash的同义词,bash的反义词,bash的例句等英语服务

Starting Bash with the --posix command-line option or executing ‘set -o posix’ while Bash is running will cause Bash to conform more closely to the POSIX standard by changing the behavior to match that specified by POSIX in areas where the Bash default differs. 1.1 What is Bash? Bash is the shell, or command language interpreter, for the GNU operating system. The name is an acronym for the 'Bourne-Again SHell', a pun on Stephen Bourne, the author of the direct ancestor of the current Unix shell sh, which appeared in the Seventh Edition Bell Labs Research version of Unix. Bash is largely compatible with sh and incorporates useful features from the. Often during an interactive session you type in a long line of text, only to notice that the first word on the line is misspelled. The Readline library gives you a set of commands for manipulating the text as you type it in, allowing you to just fix your typo, and not forcing you to retype the majority of the line. Using these editing commands, you move the cursor to the place that needs correction, and delete or insert the text of the corrections. Then, when you are satisfied with the line, you simply press RET. You do not have to be at the end of the line to press RET; the entire line is accepted regardless of the location of the cursor within the line. For the shell’s purposes, a command which exits with a zero exit status has succeeded. A non-zero exit status indicates failure. This seemingly counter-intuitive scheme is used so there is one well-defined way to indicate success and a variety of ways to indicate various failure modes. When a command terminates on a fatal signal whose number is N, Bash uses the value 128+N as the exit status.

All of the following options except for ‘disabled-builtins’, ‘direxpand-default’, and ‘xpg-echo-default’ are enabled by default, unless the operating system does not provide the necessary support. Use an emacs-style line editing interface (see Command Line Editing). This also affects the editing interface used for read -e. Bash offers several ways to repeat code—a process called looping. A for loop repeats a certain section of the code. These are useful so that a series of commands run until a particular condition is met, after which the commands stop. How to Loop Through a List

Expand the line as the shell does. This performs alias and history expansion as well as all of the shell word expansions (see Shell Expansions). Enable support for large files if the operating system requires special compiler options to build programs which can access large files. This is enabled by default, if the operating system provides large file support. This chapter briefly summarizes the shell’s ‘building blocks’: commands, control structures, shell functions, shell parameters, shell expansions, redirections, which are a way to direct input and output from and to named files, and how the shell executes commands.

A double-quoted string preceded by a dollar sign (‘$’) will cause the string to be translated according to the current locale. If the current locale is C or POSIX, the dollar sign is ignored. If the string is translated and replaced, the replacement is double-quoted. $ [[ $(( 1+1 )) -eq "2 " ]]; echo $? 0 While a string comparison of the same picks up the trailing space and therefor the string comparison fails:

A pipeline is a sequence of one or more commands separated by one of the control operators ‘|’ or ‘|&’. $if editing-mode == emacs set show-mode-in-prompt on $endif $endif This command, as seen in the previous example, terminates an $if command. If no command name results, redirections are performed, but do not affect the current shell environment. A redirection error causes the command to exit with a non-zero status. A word that has a special meaning to the shell. Most reserved words introduce shell flow control constructs, such as for and while. This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

$ string=01234567890abcdefgh $ echo ${string:7} 7890abcdefgh $ echo ${string:7:0} $ echo ${string:7:2} 78 $ echo ${string:7:-2} 7890abcdef $ echo ${string: -7} bcdefgh $ echo ${string: -7:0} $ echo ${string: -7:2} bc $ echo ${string: -7:-2} bcdef $ set -- 01234567890abcdefgh $ echo ${1:7} 7890abcdefgh $ echo ${1:7:0} $ echo ${1:7:2} 78 $ echo ${1:7:-2} 7890abcdef $ echo ${1: -7} bcdefgh $ echo ${1: -7:0} $ echo ${1: -7:2} bc $ echo ${1: -7:-2} bcdef $ array[0]=01234567890abcdefgh $ echo ${array[0]:7} 7890abcdefgh $ echo ${array[0]:7:0} $ echo ${array[0]:7:2} 78 $ echo ${array[0]:7:-2} 7890abcdef $ echo ${array[0]: -7} bcdefgh $ echo ${array[0]: -7:0} $ echo ${array[0]: -7:2} bc $ echo ${array[0]: -7:-2} bcdef If parameter is ‘@’, the result is length positional parameters beginning at offset. A negative offset is taken relative to one greater than the greatest positional parameter, so an offset of -1 evaluates to the last positional parameter. It is an expansion error if length evaluates to a number less than zero. The general way to pass numeric arguments to a command is to type meta digits before the command. If the first ‘digit’ typed is a minus sign (‘-’), then the sign of the argument will be negative. Once you have typed one meta digit to get the argument started, you can type the remainder of the digits, and then the command. For example, to give the C-d command an argument of 10, you could type ‘M-1 0 C-d’, which will delete the next ten characters on the input line.

Define bash. bash synonyms, bash pronunciation, bash translation, English dictionary definition of bash. v. bashed , bash·ing , bash·es v. tr. 1. To strike with a heavy, crushing blow: The thug bashed the hood of the car with a sledgehammer. 2. To beat or.. If ‘..’ appears in directory, it is processed by removing the immediately preceding pathname component, back to a slash or the beginning of directory. When used with [[, the ‘<’ and ‘>’ operators sort lexicographically using the current locale. If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public. If a non-empty directory name from CDPATH is used, or if ‘-’ is the first argument, and the directory change is successful, the absolute pathname of the new working directory is written to the standard output. umask [-p] [-S] [mode] Set the shell process’s file creation mask to mode. If mode begins with a digit, it is interpreted as an octal number; if not, it is interpreted as a symbolic mode mask similar to that accepted by the chmod command. If mode is omitted, the current value of the mask is printed. If the -S option is supplied without a mode argument, the mask is printed in a symbolic format. If the -p option is supplied, and mode is omitted, the output is in a form that may be reused as input. The return status is zero if the mode is successfully changed or if no mode argument is supplied, and non-zero otherwise.

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