calmsacibis995
254 lines
9.5 KiB
Groff
254 lines
9.5 KiB
Groff
'\"macro stdmacro
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.if n .pH g1.fc @(#)fc 30.2 of 12/25/85
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.nr X
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.if \nX=0 .ds x} fc 1 "Essential Utilities" "\&"
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.if \nX=1 .ds x} fc 1 "Essential Utilities"
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.if \nX=2 .ds x} fc 1 "" "\&"
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.if \nX=3 .ds x} fc "" "" "\&"
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.ds OK [\|
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.ds CK \|]
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.TH \*(x}
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.SH NAME
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\f3fc\f1 - process the command history list
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.SH SYNOPSIS
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.nf
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\f3fc [-r][-e editor] [first[last]]\f1
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\f3fc -l[-nr] [first[last]]\f1
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\f3fc -s[old=new][first]\f1
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.fi
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.SH DESCRIPTION
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The \f3fc\f1 utility lists or edits and reexecutes, commands previously
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entered to an interactive sh.
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.PP
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The command history list references commands by number. The first
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number in the list is selected arbitrarily. The relationship of a
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number to its command will not change except when the user logs in and
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no other process is accessing the list, at which time the system may
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reset the numbering to start the oldest retained command at another
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number (usually 1). When the number reaches an implementation-dependent
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upper limit, which will be no smaller than the value in \f3HISTSIZE\f1 or
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32767 (whichever is greater), the shell may wrap the numbers, starting
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the next command with a lower number (usually 1). However, despite this
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optional wrapping of numbers, \f3fc\f1 will maintain the time-ordering
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sequence of the commands. For example, if four commands in sequence are
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given the numbers 32766, 32767, 1 (wrapped), and 2 as they are
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executed, command 32767 is considered the command previous to 1, even
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though its number is higher.
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.PP
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When commands are edited (when the \f3-l\f1 option is not specified), the
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resulting lines will be entered at the end of the history list and then
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reexecuted by sh. The \f3fc\f1 command that caused the editing will not be
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entered into the history list. If the editor returns a non-zero exit
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status, this will suppress the entry into the history list and the
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command reexecution. Any command-line variable assignments or
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redirection operators used with \f3fc\f1 will affect both the \f3fc\f1 command
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itself as well as the command that results, for example:
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.TP 4
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\
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fc -s -- -1 2>/dev/null
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.PP
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reinvokes the previous command, suppressing standard error for both \f3fc\f1
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and the previous command.
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.SH OPTIONS
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The \f3fc\f1 utility supports the XBD specification, Utility Syntax
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Guidelines.
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.PP
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The following options are supported:
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.TP 12
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\f3-e editor\f1
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Use the editor named by editor to edit the commands. The editor string
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is a utility name, subject to search via the \f3PATH\f1 variable.
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The value in the \f3FCEDIT\f1
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variable is used as a default when \f3-e\f1 is not specified. If \f3FCEDIT\f1 is
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null or unset, \f3ed\f1 will be used as the editor.
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.TP
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\f3-l\f1
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(The letter ell.) List the commands rather than invoking an editor on them. The commands
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will be written in the sequence indicated by the first and last
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operands, as affected by \f3-r\f1, with each command preceded by the command
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number.
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.TP
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\f3-n\f1
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Suppress command numbers when listing with \f3-l\f1.
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.TP
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\f3-r\f1
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Reverse the order of the commands listed (with \f3-l\f1) or edited
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(with neither \f3-l\f1 nor \f3-s\f1).
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.TP
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\f3-s\f1
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Reexecute the command without invoking an editor.
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.SH OPERANDS
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The following operands are supported:
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.TP 12
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first
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.TP
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last
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Select the commands to list or edit. The number of previous
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commands that can be accessed is determined by the value of the
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\f3HISTSIZE\f1 variable. The value of \f3first\f1 or \f3last\f1 or both will be one of
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the following:
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.RS
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.TP 10
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[+]number
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A positive number representing a command number; command numbers can be
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displayed with the \f3-l\f1 option.
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.TP 10
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-number
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A negative decimal number representing the command that was executed
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number of commands previously. For example, -1 is the immediately
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previous command.
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.TP 10
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string
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A string indicating the most recently entered command that begins
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with that string. If the \f3old=new\f1 operand is not also specified with \f3-s\f1,
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the string form of the first operand cannot contain an embedded equal
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sign.
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.RE
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.TP 12
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\
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When the synopsis form with -s is used:
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.TP 16
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\
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If first is omitted, the previous command will be used.
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.TP 12
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\
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For the synopsis forms without -s:
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.TP 16
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\
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If last is omitted, last defaults to the previous command when -l is
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specified; otherwise, it defaults to first.
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.TP 16
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\
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If first and last are both omitted, the previous 16 commands will be
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listed or the previous single command will be edited (based on the -l
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option).
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.TP 16
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\
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If first and last are both present, all of the commands from first to
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last will be edited (without -l) or listed (with -l). Editing multiple
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commands will be accomplished by presenting to the editor all of the
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commands at one time, each command starting on a new line. If first
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represents a newer command than last, the commands will be listed or
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edited in reverse sequence, equivalent to using -r. For example, the
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following commands on the first line are equivalent to the
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corresponding commands on the second:
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.IP
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.nf
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fc -r 10 20 fc 30 40
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fc 20 10 fc -r 40 30
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.fi
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.TP 16
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\
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When a range of commands is used, it will not be an error to specify
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first or last values that are not in the history list; fc will
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substitute the value representing the oldest or newest command in the
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list, as appropriate. For example, if there are only ten commands in
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the history list, numbered 1 to 10:
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.IP
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.nf
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fc -l fc 1 99
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.fi
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.TP 16
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\
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will list and edit, respectively, all ten commands.
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.TP 12
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old=new
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Replace the first occurrence of string old in the commands to be
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reexecuted by the string new.
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.SH ENVIRONMENT VARIABLES
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The following environment variables affect the execution of fc:
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.TP 12
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\f3FCEDIT\f1
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This variable, when expanded by the shell, determines the default value
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for the \f3-e editor\f1 option's editor option-argument. If \f3FCEDIT\f1 is null or
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unset, \f3ed\f1 will be used as the editor.
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.TP
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\f3HISTFILE\f1
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Determine a pathname naming a command history file. If the \f3HISTFILE\f1
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variable is not set, the shell may attempt to access or create a file \f3.sh_history\f1
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in the user's home directory. If the shell cannot obtain
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both read and write access to, or create, the history file, it will use
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an unspecified mechanism that allows the history to operate properly.
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(References to history "file" in this section are understood to mean
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this unspecified mechanism in such cases.) An implementation may choose
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to access this variable only when initialising the history file; this
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initialisation will occur when \f3fc\f1 or \f3sh\f1 first attempt to retrieve
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entries from, or add entries to, the file, as the result of commands
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issued by the user, the file named by the \f3ENV\f1 variable, or
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implementation-dependent system startup files. (The initialisation
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process for the history file can be dependent on the system startup
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files, in that they may contain commands that will effectively preempt
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the user's settings of \f3HISTFILE\f1 and \f3HISTSIZE\f1. For example, function
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definition commands are recorded in the history file, unless the \f3set -o\f1
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\f3nolog\f1 option is set. If the system administrator includes function
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definitions in some system startup file called before the \f3ENV\f1 file, the
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history file will be initialised before the user gets a chance to
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influence its characteristics.) In some historical shells, the history
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file is initialised just after the \f3ENV\f1 file has been processed.
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Therefore, it is implementation-dependent whether changes made to
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\f3HISTFILE\f1 after the history file has been initialised are effective.
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Implementations may choose to disable the history list mechanism for
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users with appropriate privileges who do not set \f3HISTFILE\f ; the
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specific circumstances under which this will occur are
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implementation-dependent. If more than one instance of the shell is
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using the same history file, it is unspecified how updates to the
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history file from those shells interact. As entries are deleted from
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the history file, they will be deleted oldest first. It is unspecified
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when history file entries are physically removed from the history
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file.
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.TP
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\f3HISTSIZE\f1
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Determine a decimal number representing the limit to the number of
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previous commands that are accessible. If this variable is unset, an
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unspecified default greater than or equal to 128 will be used. The
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maximum number of commands in the history list is unspecified, but will
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be at least 128. An implementation may choose to access this variable
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only when initialising the history file, as described under \f3HISTFILE\f.
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Therefore, it is unspecified whether changes made to \f3HISTSIZE\f1 after the
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history file has been initialised are effective.
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.SH STDOUT
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When the \f3-l\f1 option is used to list commands, the format of each command
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in the list is as follows:
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.IP
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"%d\\t%s\\n", <line number>, <command>
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.PP
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If both the \f3-l\f1 and \f3-n\f1 options are specified, the format of each command
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is:
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.IP
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"\\t%s\\n", <command>
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.PP
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If the <\f3command\f1> consists of more than one line, the lines after the
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first are displayed as:
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.IP
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"\\t%s\\n", <continued-command>
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.PP
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.SH \f3EXIT STATUS\f1
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The following exit values are returned:
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.TP 4
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0
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Successful completion of the listing.
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.TP 4
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>0
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An error occurred.
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.PP
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Otherwise, the exit status will be that of the commands executed by
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\f3fc\f1.
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.SH APPLICATION USAGE
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Since editors sometimes use file descriptors as integral parts of their
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editing, redirecting their file descriptors as part of the \f3fc\f1 command
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can produce unexpected results. For example, if \f3vi\f1 is the \f3FCEDIT\f1
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editor, the command:
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.IP
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fc -s | more
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.PP
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will not work correctly on many systems.
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.PP
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Users on windowing systems may want to have separate history files for
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each window by setting HISTFILE as follows:
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.IP
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HISTFILE=$HOME/.sh_hist$$
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.SH SEE ALSO
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\f3sh(1).\f1
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