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Chet Ramey
2020-05-27 09:00:49 -04:00
parent e76c732799
commit ce1a3c07c4
102 changed files with 29297 additions and 18340 deletions
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@@ -5,12 +5,12 @@
.\" Case Western Reserve University
.\" chet.ramey@case.edu
.\"
.\" Last Change: Tue May 5 16:20:48 EDT 2020
.\" Last Change: Sat May 23 12:45:10 EDT 2020
.\"
.\" bash_builtins, strip all but Built-Ins section
.if \n(zZ=1 .ig zZ
.if \n(zY=1 .ig zY
.TH BASH 1 "2020 May 5" "GNU Bash 5.0"
.TH BASH 1 "2020 May 23" "GNU Bash 5.1"
.\"
.\" There's some problem with having a `@'
.\" in a tagged paragraph with the BSD man macros.
@@ -2034,9 +2034,9 @@ below.
.TP
.B BASH_COMPAT
The value is used to set the shell's compatibility level.
See the description of the \fBshopt\fP builtin below under
\fBSHELL BUILTIN COMMANDS\fP
for a description of the various compatibility
See
\fBSHELL COMPATIBILITY MODE\fP
below for a description of the various compatibility
levels and their effects.
The value may be a decimal number (e.g., 4.2) or an integer (e.g., 42)
corresponding to the desired compatibility level.
@@ -2045,9 +2045,12 @@ level is set to the default for the current version.
If \fBBASH_COMPAT\fP is set to a value that is not one of the valid
compatibility levels, the shell prints an error message and sets the
compatibility level to the default for the current version.
The valid compatibility levels correspond to the compatibility options
accepted by the \fBshopt\fP builtin described below (for example,
\fBcompat42\fP means that 4.2 and 42 are valid values).
The valid values correspond to the compatibility levels
described below under
\fBSHELL COMPATIBILITY MODE\fP.
For example, 4.2 and 42 are valid values that correspond
to the \fBcompat42\fP \fBshopt\fP option
and set the compatibility level to 42.
The current version is also a valid value.
.TP
.B BASH_ENV
@@ -9934,72 +9937,27 @@ This option is enabled by default, but only has an effect if command
history is enabled, as described above under
.SM
.BR HISTORY .
.PD 0
.TP 8
.B compat31
If set,
.B bash
changes its behavior to that of version 3.1 with respect to quoted
arguments to the \fB[[\fP conditional command's \fB=~\fP operator
and locale-specific string comparison when using the \fB[[\fP
conditional command's \fB<\fP and \fB>\fP operators.
Bash versions prior to bash-4.1 use ASCII collation and
.IR strcmp (3);
bash-4.1 and later use the current locale's collation sequence and
.IR strcoll (3).
.TP 8
.B compat32
If set,
.B bash
changes its behavior to that of version 3.2 with respect to
locale-specific string comparison when using the \fB[[\fP
conditional command's \fB<\fP and \fB>\fP operators (see previous item)
and the effect of interrupting a command list.
Bash versions 3.2 and earlier continue with the next command in the list
after one terminates due to an interrupt.
.TP 8
.B compat40
If set,
.B bash
changes its behavior to that of version 4.0 with respect to locale-specific
string comparison when using the \fB[[\fP
conditional command's \fB<\fP and \fB>\fP operators (see description of
\fBcompat31\fP)
and the effect of interrupting a command list.
Bash versions 4.0 and later interrupt the list as if the shell received the
interrupt; previous versions continue with the next command in the list.
.TP 8
.B compat41
If set,
.BR bash ,
when in \fIposix mode\fP, treats a single quote in a double-quoted
parameter expansion as a special character. The single quotes must match
(an even number) and the characters between the single quotes are considered
quoted. This is the behavior of <posix mode through version 4.1.
The default bash behavior remains as in previous versions.
.TP 8
.B compat42
If set,
.B bash
does not process the replacement string in the pattern substitution word
expansion using quote removal.
.TP 8
.B compat43
If set,
.B bash
does not print a warning message if an attempt is made to use a quoted compound
array assignment as an argument to \fBdeclare\fP,
makes word expansion errors
non-fatal errors that cause the current command to fail (the default behavior is
to make them fatal errors that cause the shell to exit),
and does not reset the
loop state when a shell function is executed (this allows \fBbreak\fP or
\fBcontinue\fP in a shell function to affect loops in the caller's context).
.TP 8
.B compat44
If set,
.B bash
saves the positional parameters to BASH_ARGV and BASH_ARGC before they are
used, regardless of whether or not extended debugging mode is enabled.
.PD
These control aspects of the shell's compatibility mode
(see
.SM
.B "SHELL COMPATIBILITY MODE"
below).
.TP 8
.B complete_fullquote
If set,
@@ -10906,6 +10864,199 @@ If
specifies a non-existent process or job, the return status is
127. Otherwise, the return status is the exit status of the last
process or job waited for.
.SH "SHELL COMPATIBILITY MODE"
Bash-4.0 introduced the concept of a `shell compatibility level', specified
as a set of options to the shopt builtin
.BR compat31 ,
.BR compat32 ,
.BR compat40 ,
.BR compat41 ,
and so on).
There is only one current
compatibility level -- each option is mutually exclusive.
The compatibility level is intended to allow users to select behavior
from previous versions that is incompatible with newer versions
while they migrate scripts to use current features and
behavior. It's intended to be a temporary solution.
.PP
This section does not mention behavior that is standard for a particular
version (e.g., setting \fBcompat32\fP means that quoting the rhs of the regexp
matching operator quotes special regexp characters in the word, which is
default behavior in bash-3.2 and above).
.PP
If a user enables, say, \fBcompat32\fP, it may affect the behavior of other
compatibility levels up to and including the current compatibility level.
The idea is that each compatibility level controls behavior that changed
in that version of \fBbash\fP,
but that behavior may have been present in earlier versions.
For instance, the change to use locale-based comparisons with the \fB[[\fP
command came in bash-4.1, and earlier versions used ASCII-based comparisons,
so enabling \fBcompat32\fP will enable ASCII-based comparisons as well.
That granularity may not be sufficient for
all uses, and as a result users should employ compatibility levels carefully.
Read the documentation for a particular feature to find out the
current behavior.
.PP
Bash-4.3 introduced a new shell variable:
.SM
.BR BASH_COMPAT .
The value assigned
to this variable (a decimal version number like 4.2, or an integer
corresponding to the \fBcompat\fP\fINN\fP option, like 42) determines the
compatibility level.
.PP
Starting with bash-4.4, Bash has begun deprecating older compatibility
levels.
Eventually, the options will be removed in favor of
.SM
.BR BASH_COMPAT .
.PP
Bash-5.0 is the final version for which there will be an individual shopt
option for the previous version. Users should use
.SM
.B BASH_COMPAT
on bash-5.0 and later versions.
.PP
The following table describes the behavior changes controlled by each
compatibility level setting.
The \fBcompat\fP\fINN\fP tag is used as shorthand for setting the
compatibility level
to \fINN\fP using one of the following mechanisms.
For versions prior to bash-5.0, the compatibility level may be set using
the corresponding \fBcompat\fP\fINN\fP shopt option.
For bash-4.3 and later versions, the
.SM
.B BASH_COMPAT
variable is preferred,
and it is required for bash-5.1 and later versions.
.TP
\fBcompat31\fP
.PD 0
.RS
.IP \(bu
quoting the rhs of the \fB[[\fP command's regexp matching operator (=~)
has no special effect
.RE
.PD
.TP
\fBcompat32\fP
.PD 0
.RS
.IP \(bu
interrupting a command list such as "a ; b ; c" causes the execution
of the next command in the list (in bash-4.0 and later versions,
the shell acts as if it received the interrupt, so
interrupting one command in a list aborts the execution of the
entire list)
.RE
.PD
.TP
\fBcompat40\fP
.PD 0
.RS
.IP \(bu
the \fB<\fP and \fB>\fP operators to the \fB[[\fP command do not
consider the current locale when comparing strings; they use ASCII
ordering.
Bash versions prior to bash-4.1 use ASCII collation and
.IR strcmp (3);
bash-4.1 and later use the current locale's collation sequence and
.IR strcoll (3).
.RE
.PD
.TP
\fBcompat41\fP
.PD 0
.RS
.IP \(bu
in \fIposix\fP mode, \fBtime\fP may be followed by options and still be
recognized as a reserved word (this is POSIX interpretation 267)
.IP \(bu
in \fIposix\fP mode, the parser requires that an even number of single
quotes occur in the \fIword\fP portion of a double-quoted
parameter expansion and treats them specially, so that characters within
the single quotes are considered quoted
(this is POSIX interpretation 221)
.RE
.PD
.TP
\fBcompat42\fP
.PD 0
.RS
.IP \(bu
the replacement string in double-quoted pattern substitution does not
undergo quote removal, as it does in versions after bash-4.2
.IP \(bu
in posix mode, single quotes are considered special when expanding
the \fIword\fP portion of a double-quoted parameter expansion
and can be used to quote a closing brace or other special character
(this is part of POSIX interpretation 221);
in later versions, single quotes
are not special within double-quoted word expansions
.RE
.PD
.TP
\fBcompat43\fP
.PD 0
.RS
.IP \(bu
the shell does not print a warning message if an attempt is made to
use a quoted compound assignment as an argument to declare
(declare -a foo='(1 2)'). Later versions warn that this usage is
deprecated
.IP \(bu
word expansion errors are considered non-fatal errors that cause the
current command to fail, even in posix mode
(the default behavior is to make them fatal errors that cause the shell
to exit)
.IP \(bu
when executing a shell function, the loop state (while/until/etc.)
is not reset, so \fBbreak\fP or \fBcontinue\fP in that function will break
or continue loops in the calling context. Bash-4.4 and later reset
the loop state to prevent this
.RE
.PD
.TP
\fBcompat44\fP
.PD 0
.RS
.IP \(bu
the shell sets up the values used by
.SM
.B BASH_ARGV
and
.SM
.B BASH_ARGC
so they can expand to the shell's positional parameters even if extended
debugging mode is not enabled
.IP \(bu
a subshell inherits loops from its parent context, so \fBbreak\fP
or \fBcontinue\fP will cause the subshell to exit.
Bash-5.0 and later reset the loop state to prevent the exit
.IP \(bu
variable assignments preceding builtins like \fBexport\fP and \fBreadonly\fP
that set attributes continue to affect variables with the same
name in the calling environment even if the shell is not in posix
mode
.RE
.PD
.TP
\fBcompat50\fP
.PD 0
.RS
.IP \(bu
Bash-5.1 changed the way
.SM
.B $RANDOM
is generated to introduce slightly
more randomness. If the shell compatibility level is set to 50 or
lower, it reverts to the method from bash-5.0 and previous versions,
so seeding the random number generator by assigning a value to
.SM
.B RANDOM
will produce the same sequence as in bash-5.0
.RE
.PD
.\" bash_builtins
.if \n(zZ=1 .ig zZ
.SH "RESTRICTED SHELL"