Imported from ../bash-2.03.tar.gz.
This commit is contained in:
Jari Aalto
parent
bc4cd23ce9
commit
b72432fdcc
191 changed files with 10113 additions and 3553 deletions
306
doc/FAQ
306
doc/FAQ
|
|
@ -1,4 +1,4 @@
|
|||
This is the Bash FAQ, version 2.13, for Bash version 2.02.
|
||||
This is the Bash FAQ, version 3.0, for Bash version 2.03.
|
||||
|
||||
This document contains a set of frequently-asked questions concerning
|
||||
Bash, the GNU Bourne-Again Shell. Bash is a freely-available command
|
||||
|
|
@ -20,87 +20,87 @@ Contents:
|
|||
|
||||
Section A: The Basics
|
||||
|
||||
1) What is it?
|
||||
2) What's the latest version?
|
||||
3) Where can I get it?
|
||||
4) On what machines will bash run?
|
||||
5) Will bash run on operating systems other than Unix?
|
||||
6) How can I build bash with gcc?
|
||||
7) How can I make bash my login shell?
|
||||
8) I just changed my login shell to bash, and now I can't FTP into my
|
||||
machine. Why not?
|
||||
9) What's the `POSIX 1003.2 standard'?
|
||||
10) What is the bash `posix mode'?
|
||||
A1) What is it?
|
||||
A2) What's the latest version?
|
||||
A3) Where can I get it?
|
||||
A4) On what machines will bash run?
|
||||
A5) Will bash run on operating systems other than Unix?
|
||||
A6) How can I build bash with gcc?
|
||||
A7) How can I make bash my login shell?
|
||||
A8) I just changed my login shell to bash, and now I can't FTP into my
|
||||
machine. Why not?
|
||||
A9) What's the `POSIX 1003.2 standard'?
|
||||
A10) What is the bash `posix mode'?
|
||||
|
||||
Section B: The latest version
|
||||
|
||||
11) What's new in version 2.02?
|
||||
12) Are there any user-visible incompatibilities between bash-2.02 and
|
||||
B1) What's new in version 2.03?
|
||||
B2) Are there any user-visible incompatibilities between bash-2.03 and
|
||||
bash-1.14.7?
|
||||
|
||||
Section C: Differences from other Unix shells
|
||||
|
||||
13) How does bash differ from sh, the Bourne shell?
|
||||
14) How does bash differ from the Korn shell, version ksh88?
|
||||
15) Which new features in ksh-93 are not in bash, and which are?
|
||||
C1) How does bash differ from sh, the Bourne shell?
|
||||
C2) How does bash differ from the Korn shell, version ksh88?
|
||||
C3) Which new features in ksh-93 are not in bash, and which are?
|
||||
|
||||
Section D: Why does bash do some things differently than other Unix shells?
|
||||
|
||||
16) Why does bash run a different version of `command' than
|
||||
D1) Why does bash run a different version of `command' than
|
||||
`which command' says it will?
|
||||
17) Why doesn't bash treat brace expansions exactly like csh?
|
||||
18) Why doesn't bash have csh variable modifiers?
|
||||
19) How can I make my csh aliases work when I convert to bash?
|
||||
20) How can I pipe standard output and standard error from one command to
|
||||
D2) Why doesn't bash treat brace expansions exactly like csh?
|
||||
D3) Why doesn't bash have csh variable modifiers?
|
||||
D4) How can I make my csh aliases work when I convert to bash?
|
||||
D5) How can I pipe standard output and standard error from one command to
|
||||
another, like csh does with `|&'?
|
||||
21) Now that I've converted from ksh to bash, are there equivalents to
|
||||
D6) Now that I've converted from ksh to bash, are there equivalents to
|
||||
ksh features like autoloaded functions and the `whence' command?
|
||||
|
||||
Section E: How can I get bash to do certain things, and why does bash do
|
||||
things the way it does?
|
||||
|
||||
22) Why is the bash builtin `test' slightly different from /bin/test?
|
||||
23) Why does bash sometimes say `Broken pipe'?
|
||||
24) How can I get bash to read and display eight-bit characters?
|
||||
25) How do I write a function `x' to replace builtin command `x', but
|
||||
E1) Why is the bash builtin `test' slightly different from /bin/test?
|
||||
E2) Why does bash sometimes say `Broken pipe'?
|
||||
E3) How can I get bash to read and display eight-bit characters?
|
||||
E4) How do I write a function `x' to replace builtin command `x', but
|
||||
still invoke the command from within the function?
|
||||
26) When I have terminal escape sequences in my prompt, why does bash
|
||||
E5) When I have terminal escape sequences in my prompt, why does bash
|
||||
wrap lines at the wrong column?
|
||||
27) How can I find the value of a shell variable whose name is the value
|
||||
E6) How can I find the value of a shell variable whose name is the value
|
||||
of another shell variable?
|
||||
28) If I pipe the output of a command into `read variable', why doesn't
|
||||
E7) If I pipe the output of a command into `read variable', why doesn't
|
||||
the output show up in $variable when the read command finishes?
|
||||
29) I have a bunch of shell scripts that use backslash-escaped characters
|
||||
E8) I have a bunch of shell scripts that use backslash-escaped characters
|
||||
in arguments to `echo'. Bash doesn't interpret these characters. Why
|
||||
not, and how can I make it understand them?
|
||||
30) Why doesn't a while or for loop get suspended when I type ^Z?
|
||||
31) How can I make the bash `time' reserved word print timing output that
|
||||
looks like the output from my system's /usr/bin/time?
|
||||
E9) Why doesn't a while or for loop get suspended when I type ^Z?
|
||||
E10) How can I make the bash `time' reserved word print timing output that
|
||||
looks like the output from my system's /usr/bin/time?
|
||||
|
||||
Section F: Things to watch out for on certain Unix versions
|
||||
|
||||
32) Why can't I use command line editing in my `cmdtool'?
|
||||
33) I built bash on Solaris 2. Why do globbing expansions and filename
|
||||
F1) Why can't I use command line editing in my `cmdtool'?
|
||||
F2) I built bash on Solaris 2. Why do globbing expansions and filename
|
||||
completion chop off the first few characters of each filename?
|
||||
34) Why does bash dump core after I interrupt username completion or
|
||||
F3) Why does bash dump core after I interrupt username completion or
|
||||
`~user' tilde expansion on a machine running NIS?
|
||||
35) I'm running SVR4.2. Why is the line erased every time I type `@'?
|
||||
36) Why does bash report syntax errors when my C News scripts use a
|
||||
F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
|
||||
F5) Why does bash report syntax errors when my C News scripts use a
|
||||
redirection before a subshell command?
|
||||
|
||||
Section G: Where do I go from here?
|
||||
|
||||
37) How do I report bugs in bash, and where should I look for fixes and
|
||||
G1) How do I report bugs in bash, and where should I look for fixes and
|
||||
advice?
|
||||
38) What kind of bash documentation is there?
|
||||
39) What's coming in future versions?
|
||||
40) What's on the bash `wish list'?
|
||||
41) When will the next release appear?
|
||||
G2) What kind of bash documentation is there?
|
||||
G3) What's coming in future versions?
|
||||
G4) What's on the bash `wish list'?
|
||||
G5) When will the next release appear?
|
||||
|
||||
----------
|
||||
Section A: The Basics
|
||||
|
||||
1) What is it?
|
||||
A1) What is it?
|
||||
|
||||
Bash is a Unix command interpreter (shell). It is an implementation of
|
||||
the Posix 1003.2 shell standard, and resembles the Korn and System V
|
||||
|
|
@ -118,26 +118,26 @@ Bash was originally written by Brian Fox of the Free Software
|
|||
Foundation. The current developer and maintainer is Chet Ramey
|
||||
of Case Western Reserve University.
|
||||
|
||||
2) What's the latest version?
|
||||
A2) What's the latest version?
|
||||
|
||||
The latest version is 2.02, first made available on Monday, 20 April, 1998.
|
||||
The latest version is 2.03, first made available on Friday, 19 Feburary 1999.
|
||||
|
||||
3) Where can I get it?
|
||||
A3) Where can I get it?
|
||||
|
||||
Bash is the GNU project's shell, and so is available from the
|
||||
master GNU archive site, prep.ai.mit.edu, and its mirrors. The
|
||||
master GNU archive site, ftp.gnu.org, and its mirrors. The
|
||||
latest version is also available for FTP from ftp.cwru.edu.
|
||||
The following URLs tell how to get version 2.02:
|
||||
The following URLs tell how to get version 2.03:
|
||||
|
||||
ftp://prep.ai.mit.edu/pub/gnu/bash-2.02.tar.gz
|
||||
ftp://ftp.cwru.edu/pub/bash/bash-2.02.tar.gz
|
||||
ftp://ftp.gnu.org/pub/gnu/bash-2.03.tar.gz
|
||||
ftp://ftp.cwru.edu/pub/bash/bash-2.03.tar.gz
|
||||
|
||||
Formatted versions of the documentation are available with the URLs:
|
||||
|
||||
ftp://prep.ai.mit.edu/pub/gnu/bash-doc-2.02.tar.gz
|
||||
ftp://ftp.cwru.edu/pub/bash/bash-doc-2.02.tar.gz
|
||||
ftp://ftp.gnu.org/pub/gnu/bash-doc-2.03.tar.gz
|
||||
ftp://ftp.cwru.edu/pub/bash/bash-doc-2.03.tar.gz
|
||||
|
||||
4) On what machines will bash run?
|
||||
A4) On what machines will bash run?
|
||||
|
||||
Bash has been ported to nearly every version of UNIX. All you
|
||||
should have to do to build it on a machine for which a port
|
||||
|
|
@ -147,10 +147,10 @@ itself accordingly, using a script created by GNU autoconf.
|
|||
|
||||
More information appears in the file `INSTALL' in the distribution.
|
||||
|
||||
5) Will bash run on operating systems other than Unix?
|
||||
A5) Will bash run on operating systems other than Unix?
|
||||
|
||||
Configuration specifics for Unix-like systems such as QNX and
|
||||
LynxOS are included in the distribution. Bash-2.02 should
|
||||
LynxOS are included in the distribution. Bash-2.03 should
|
||||
compile and run on Minix 2.0 (patches were contributed), but I
|
||||
don't believe anyone has built bash-2.x on earlier Minix versions
|
||||
yet.
|
||||
|
|
@ -162,12 +162,12 @@ project. For more information about the project, look at the URL
|
|||
|
||||
http://www.cygnus.com/misc/gnu-win32
|
||||
|
||||
Cygnus has ported bash-1.14.7, and their port is part of the current
|
||||
gnu-win32 release. Cygnus has also done a port of bash-2.01 to the
|
||||
GNU-Win32 environment, and it should be available as part of their next
|
||||
release.
|
||||
Cygnus originally ported bash-1.14.7, and that port was part of their
|
||||
early GNU-Win32 releases. Cygnus has also done a port of bash-2.01 to the
|
||||
GNU-Win32 environment, and it is available as part of their current
|
||||
release. (They may have upgraded by now.)
|
||||
|
||||
Bash-2.02 should require no local Cygnus changes to build and run under
|
||||
Bash-2.03 should require no local Cygnus changes to build and run under
|
||||
GNU-WIN32.
|
||||
|
||||
The Cygnus port works only on Intel machines. There is a port of bash
|
||||
|
|
@ -175,9 +175,19 @@ The Cygnus port works only on Intel machines. There is a port of bash
|
|||
|
||||
ftp://ftp.gnustep.org//pub/win32/bash-alpha-nt-1.01.tar.gz
|
||||
|
||||
Softway Systems has ported bash-2.01.1 to their Interix (nee OpenNT)
|
||||
Softway Systems has ported bash-2.01 to their Interix (nee OpenNT)
|
||||
system, a Unix subsystem for NT that replaces the Microsoft POSIX
|
||||
subsystem. Check out http://www.interix.com for more information.
|
||||
Some support for Interix has been incorporated into bash, beginning
|
||||
with Bash-2.03. It should be easier to build bash on Interix now,
|
||||
but Interix users should fetch
|
||||
|
||||
ftp://ftp.interix.com/pub/tw/unsup/bash.diffs.tar.gz
|
||||
|
||||
and read the README.OpenNT file in that archive. It will detail the
|
||||
arguments configure needs to build on Interix. A configure cache
|
||||
file for Interix is in the bash distribution in cross-build/opennt.cache;
|
||||
copy that to `config.cache' before starting configure.
|
||||
|
||||
D. J. Delorie has ported bash-1.14.7 to run under MS-DOS, as part of
|
||||
the DJGPP project. For more information on the project, see
|
||||
|
|
@ -201,12 +211,12 @@ ftp://hobbes.nmsu.edu/pub/os2/util/shell/bash-2.0(253).zip
|
|||
I haven't looked at either, but the second appears to be a binary-only
|
||||
distribution. Beware.
|
||||
|
||||
6) How can I build bash with gcc?
|
||||
A6) How can I build bash with gcc?
|
||||
|
||||
Bash configures to use gcc by default if it is available. Read the
|
||||
file INSTALL in the distribution for more information.
|
||||
|
||||
7) How can I make bash my login shell?
|
||||
A7) How can I make bash my login shell?
|
||||
|
||||
Some machines let you use `chsh' to change your login shell. Other
|
||||
systems use `passwd -s' or `passwd -e'. If one of these works for
|
||||
|
|
@ -252,7 +262,7 @@ This will cause login shells to replace themselves with bash running as
|
|||
a login shell. Once you have this working, you can copy your initialization
|
||||
code from ~/.profile to ~/.bash_profile.
|
||||
|
||||
8) I just changed my login shell to bash, and now I can't FTP into my
|
||||
A8) I just changed my login shell to bash, and now I can't FTP into my
|
||||
machine. Why not?
|
||||
|
||||
You must add the full pathname to bash to the file /etc/shells. As
|
||||
|
|
@ -262,7 +272,7 @@ this before you can make bash your login shell.
|
|||
Most versions of ftpd use this file to prohibit `special' users
|
||||
such as `uucp' and `news' from using FTP.
|
||||
|
||||
9) What's the `POSIX 1003.2 standard'?
|
||||
A9) What's the `POSIX 1003.2 standard'?
|
||||
|
||||
POSIX is a name originally coined by Richard Stallman for a
|
||||
family of open system standards based on UNIX. There are a
|
||||
|
|
@ -297,7 +307,7 @@ line editing. Only vi-style line editing commands have been
|
|||
standardized; emacs editing commands were left out due to
|
||||
objections.
|
||||
|
||||
10) What is the bash `posix mode'?
|
||||
A10) What is the bash `posix mode'?
|
||||
|
||||
Although bash is an implementation of the POSIX.2 shell
|
||||
specification, there are areas where the bash default behavior
|
||||
|
|
@ -314,9 +324,29 @@ Reference Manual.
|
|||
|
||||
Section B: The latest version
|
||||
|
||||
11) What's new in version 2.02?
|
||||
B1) What's new in version 2.03?
|
||||
|
||||
Bash-2.02 has a number of new features. Here's a short list:
|
||||
Bash-2.03 has a very few new features, in keeping with the convention
|
||||
that odd-numbered releases provide mainly bug fixes. A number of new
|
||||
features were added to Readline, mostly at the request of the Cygnus
|
||||
folks.
|
||||
|
||||
a new shopt option, `restricted_shell', so that startup files can test
|
||||
whether or not the shell was started in restricted mode
|
||||
filename generation is now performed on the words between ( and ) in
|
||||
compound array assignments (this is really a bug fix)
|
||||
OLDPWD is now auto-exported, as POSIX.2 requires
|
||||
ENV and BASH_ENV are read-only variables in a restricted shell
|
||||
Bash may now be linked against an already-installed Readline library,
|
||||
as long as the Readline library is version 4 or newer
|
||||
All shells begun with the `--login' option will source the login shell
|
||||
startup files, even if the shell is not interactive
|
||||
|
||||
There are lots of changes to the version of the Readline library released
|
||||
along with Bash-2.03. For a complete list of the changes, read the file
|
||||
CHANGES in the Bash-2.03 distribution.
|
||||
|
||||
Bash-2.02 contained the following new features:
|
||||
|
||||
a new version of malloc (based on the old GNU malloc code in previous
|
||||
bash versions) that is more page-oriented, more conservative
|
||||
|
|
@ -382,15 +412,15 @@ grammar tighter and smaller (66 reduce-reduce conflicts gone)
|
|||
lots of code now smaller and faster
|
||||
test suite greatly expanded
|
||||
|
||||
12) Are there any user-visible incompatibilities between bash-2.02 and
|
||||
B2) Are there any user-visible incompatibilities between bash-2.03 and
|
||||
bash-1.14.7?
|
||||
|
||||
There are a few incompatibilities between version 1.14.7 and version 2.02.
|
||||
They are detailed in the file COMPAT in the bash-2.02 distribution.
|
||||
There are a few incompatibilities between version 1.14.7 and version 2.03.
|
||||
They are detailed in the file COMPAT in the bash-2.03 distribution.
|
||||
|
||||
Section C: Differences from other Unix shells
|
||||
|
||||
13) How does bash differ from sh, the Bourne shell?
|
||||
C1) How does bash differ from sh, the Bourne shell?
|
||||
|
||||
This is a non-comprehensive list of features that differentiate bash
|
||||
from the SVR4.2 shell. The bash manual page explains these more
|
||||
|
|
@ -481,11 +511,12 @@ Implementation differences:
|
|||
bash allows multiple option arguments when invoked (e.g. -x -v);
|
||||
sh allows only a single option argument (`sh -x -v' attempts
|
||||
to open a file named `-v', and, on SunOS 4.1.4, dumps core.
|
||||
On Solaris 2, sh goes into an infinite loop.)
|
||||
On Solaris 2.4 and earlier versions, sh goes into an infinite
|
||||
loop.)
|
||||
sh exits a script if any builtin fails; bash exits only if one of
|
||||
the POSIX.2 `special' builtins fails
|
||||
|
||||
14) How does bash differ from the Korn shell, version ksh88?
|
||||
C2) How does bash differ from the Korn shell, version ksh88?
|
||||
|
||||
Things bash has or uses that ksh88 does not:
|
||||
long invocation options
|
||||
|
|
@ -541,9 +572,9 @@ Implementation differences:
|
|||
bash has exported functions
|
||||
bash command search finds functions before builtins
|
||||
|
||||
15) Which new features in ksh-93 are not in bash, and which are?
|
||||
C3) Which new features in ksh-93 are not in bash, and which are?
|
||||
|
||||
New things in ksh-93 not in bash-2.02:
|
||||
New things in ksh-93 not in bash-2.03:
|
||||
associative arrays
|
||||
floating point arithmetic
|
||||
++, --, comma arithmetic operators
|
||||
|
|
@ -564,7 +595,7 @@ New things in ksh-93 not in bash-2.02:
|
|||
read -t/-d
|
||||
`.' can execute shell functions
|
||||
|
||||
New things in ksh-93 present in bash-2.02:
|
||||
New things in ksh-93 present in bash-2.03:
|
||||
?: arithmetic operator
|
||||
expansions: ${!param}, ${param:offset[:len]}, ${param/pat[/str]}
|
||||
compound array assignment
|
||||
|
|
@ -588,16 +619,37 @@ New things in ksh-93 present in bash-2.02:
|
|||
|
||||
Section D: Why does bash do some things differently than other Unix shells?
|
||||
|
||||
16) Why does bash run a different version of `command' than
|
||||
D1) Why does bash run a different version of `command' than
|
||||
`which command' says it will?
|
||||
|
||||
`which' is actually a csh script that assumes you're running csh.
|
||||
It reads the csh startup files from your home directory and uses
|
||||
those to determine which `command' will be invoked. Since bash
|
||||
doesn't use any of those startup files, there's a good chance
|
||||
that your bash environment differs from your csh environment.
|
||||
On many systems, `which' is actually a csh script that assumes
|
||||
you're running csh. In tcsh, `which' and its cousin `where'
|
||||
are builtins. On other Unix systems, `which' is a perl script
|
||||
that uses the PATH environment variable.
|
||||
|
||||
17) Why doesn't bash treat brace expansions exactly like csh?
|
||||
The csh script version reads the csh startup files from your
|
||||
home directory and uses those to determine which `command' will
|
||||
be invoked. Since bash doesn't use any of those startup files,
|
||||
there's a good chance that your bash environment differs from
|
||||
your csh environment. The bash `type' builtin does everything
|
||||
`which' does, and will report correct results for the running
|
||||
shell. If you're really wedded to the name `which', try adding
|
||||
the following function definition to your .bashrc:
|
||||
|
||||
which()
|
||||
{
|
||||
builtin type -p "$@"
|
||||
}
|
||||
|
||||
If you're moving from tcsh and would like to bring `where' along
|
||||
as well, use this function:
|
||||
|
||||
where()
|
||||
{
|
||||
builtin type -a "$@"
|
||||
}
|
||||
|
||||
D2) Why doesn't bash treat brace expansions exactly like csh?
|
||||
|
||||
The only difference between bash and csh brace expansion is that
|
||||
bash requires a brace expression to contain at least one unquoted
|
||||
|
|
@ -608,7 +660,7 @@ compatibility.
|
|||
|
||||
Bash, ksh, zsh, and pd-ksh all implement brace expansion this way.
|
||||
|
||||
18) Why doesn't bash have csh variable modifiers?
|
||||
D3) Why doesn't bash have csh variable modifiers?
|
||||
|
||||
Posix has specified a more powerful, albeit somewhat more cryptic,
|
||||
mechanism cribbed from ksh, and bash implements it.
|
||||
|
|
@ -663,7 +715,7 @@ Given
|
|||
$b:e ${b##*.} xxx
|
||||
|
||||
|
||||
19) How can I make my csh aliases work when I convert to bash?
|
||||
D4) How can I make my csh aliases work when I convert to bash?
|
||||
|
||||
Bash uses a different syntax to support aliases than csh does.
|
||||
The details can be found in the documentation. We have provided
|
||||
|
|
@ -706,7 +758,7 @@ simply `cshtobash' to convert your normal interactive
|
|||
environment, or as `cshtobash ~/.login' to convert your login
|
||||
environment.
|
||||
|
||||
20) How can I pipe standard output and standard error from one command to
|
||||
D5) How can I pipe standard output and standard error from one command to
|
||||
another, like csh does with `|&'?
|
||||
|
||||
Use
|
||||
|
|
@ -716,7 +768,7 @@ The key is to remember that piping is performed before redirection, so
|
|||
file descriptor 1 points to the pipe when it is duplicated onto file
|
||||
descriptor 2.
|
||||
|
||||
21) Now that I've converted from ksh to bash, are there equivalents to
|
||||
D6) Now that I've converted from ksh to bash, are there equivalents to
|
||||
ksh features like autoloaded functions and the `whence' command?
|
||||
|
||||
There are features in ksh-88 that do not have direct bash equivalents.
|
||||
|
|
@ -735,7 +787,7 @@ read var?prompt read -p prompt var
|
|||
Section E: How can I get bash to do certain things, and why does bash do
|
||||
things the way it does?
|
||||
|
||||
22) Why is the bash builtin `test' slightly different from /bin/test?
|
||||
E1) Why is the bash builtin `test' slightly different from /bin/test?
|
||||
|
||||
The specific example used here is [ ! x -o x ], which is false.
|
||||
|
||||
|
|
@ -764,7 +816,7 @@ of the 3 Arg case.
|
|||
|
||||
As you can see, the test becomes (not (x or x)), which is false.
|
||||
|
||||
23) Why does bash sometimes say `Broken pipe'?
|
||||
E2) Why does bash sometimes say `Broken pipe'?
|
||||
|
||||
If a sequence of commands appears in a pipeline, and one of the
|
||||
reading commands finishes before the writer has finished, the
|
||||
|
|
@ -779,7 +831,11 @@ will try to write on a pipe without a reader. In that case, bash
|
|||
will print `Broken pipe' to stderr when ps is killed by a
|
||||
SIGPIPE.
|
||||
|
||||
24) How can I get bash to read and display eight-bit characters?
|
||||
You can build a version of bash that will not report SIGPIPE errors
|
||||
by uncommenting the definition of DONT_REPORT_SIGPIPE in the file
|
||||
config-top.h.
|
||||
|
||||
E3) How can I get bash to read and display eight-bit characters?
|
||||
|
||||
This is a process requiring several steps.
|
||||
|
||||
|
|
@ -813,7 +869,7 @@ this. These variables can be set in your .inputrc or using the bash
|
|||
The `set' commands between the single quotes may also be placed
|
||||
in ~/.inputrc.
|
||||
|
||||
25) How do I write a function `x' to replace builtin command `x', but
|
||||
E4) How do I write a function `x' to replace builtin command `x', but
|
||||
still invoke the command from within the function?
|
||||
|
||||
This is why the `command' and `builtin' builtins exist. The
|
||||
|
|
@ -834,7 +890,7 @@ something like the following:
|
|||
This could also be written using `command' instead of `builtin';
|
||||
the version above is marginally more efficient.
|
||||
|
||||
26) When I have terminal escape sequences in my prompt, why does bash
|
||||
E5) When I have terminal escape sequences in my prompt, why does bash
|
||||
wrap lines at the wrong column?
|
||||
|
||||
Readline, the line editing library that bash uses, does not know
|
||||
|
|
@ -850,10 +906,10 @@ characters in the prompt strings take up no screen space.
|
|||
Use the \[ escape to begin a sequence of non-printing characters,
|
||||
and the \] escape to signal the end of such a sequence.
|
||||
|
||||
27) How can I find the value of a shell variable whose name is the value
|
||||
E6) How can I find the value of a shell variable whose name is the value
|
||||
of another shell variable?
|
||||
|
||||
Bash-2.02 supports this directly. You can use
|
||||
Versions of Bash newer than Bash-2.0 support this directly. You can use
|
||||
|
||||
${!var}
|
||||
|
||||
|
|
@ -875,13 +931,13 @@ parameter:
|
|||
|
||||
The expansion of the quoted portions of this expression will be
|
||||
deferred until `eval' runs, while the `$#' will be expanded
|
||||
before `eval' is executed. In bash-2.02,
|
||||
before `eval' is executed. In versions of bash later than bash-2.0,
|
||||
|
||||
echo ${!#}
|
||||
|
||||
does the same thing.
|
||||
|
||||
28) If I pipe the output of a command into `read variable', why doesn't
|
||||
E7) If I pipe the output of a command into `read variable', why doesn't
|
||||
the output show up in $variable when the read command finishes?
|
||||
|
||||
This has to do with the parent-child relationship between Unix
|
||||
|
|
@ -937,7 +993,7 @@ this.
|
|||
This is the general approach -- in most cases you will not need to
|
||||
set $IFS to a different value.
|
||||
|
||||
29) I have a bunch of shell scripts that use backslash-escaped characters
|
||||
E8) I have a bunch of shell scripts that use backslash-escaped characters
|
||||
in arguments to `echo'. Bash doesn't interpret these characters. Why
|
||||
not, and how can I make it understand them?
|
||||
|
||||
|
|
@ -957,7 +1013,7 @@ configure with the --enable-usg-echo-default option to turn this
|
|||
on. Be aware that this will cause some of the tests run when you
|
||||
type `make tests' to fail.
|
||||
|
||||
30) Why doesn't a while or for loop get suspended when I type ^Z?
|
||||
E9) Why doesn't a while or for loop get suspended when I type ^Z?
|
||||
|
||||
This is a consequence of how job control works on Unix. The only
|
||||
thing that can be suspended is the process group. This is a single
|
||||
|
|
@ -972,8 +1028,8 @@ If you want to be able to stop the entire loop, you need to put it
|
|||
within parentheses, which will force the loop into a subshell that
|
||||
may be stopped (and subsequently restarted) as a single unit.
|
||||
|
||||
31) How can I make the bash `time' reserved word print timing output that
|
||||
looks like the output from my system's /usr/bin/time?
|
||||
E10) How can I make the bash `time' reserved word print timing output that
|
||||
looks like the output from my system's /usr/bin/time?
|
||||
|
||||
The bash command timing code looks for a variable `TIMEFORMAT' and
|
||||
uses its value as a format string to decide how to display the
|
||||
|
|
@ -1006,7 +1062,7 @@ The ksh format can be emulated with:
|
|||
|
||||
Section F: Things to watch out for on certain Unix versions
|
||||
|
||||
32) Why can't I use command line editing in my `cmdtool'?
|
||||
F1) Why can't I use command line editing in my `cmdtool'?
|
||||
|
||||
The problem is `cmdtool' and bash fighting over the input. When
|
||||
scrolling is enabled in a cmdtool window, cmdtool puts the tty in
|
||||
|
|
@ -1034,7 +1090,7 @@ The bash command-line editing should behave better in the new
|
|||
cmdtool. If this works, you can put the assignment to TERMCAP
|
||||
in your bashrc file.
|
||||
|
||||
33) I built bash on Solaris 2. Why do globbing expansions and filename
|
||||
F2) I built bash on Solaris 2. Why do globbing expansions and filename
|
||||
completion chop off the first few characters of each filename?
|
||||
|
||||
This is the consequence of building bash on SunOS 5 and linking
|
||||
|
|
@ -1054,7 +1110,7 @@ If you have installed the Sun C compiler, you may also need to
|
|||
put /usr/ccs/bin and /opt/SUNWspro/bin into your $PATH before
|
||||
/usr/ucb.
|
||||
|
||||
34) Why does bash dump core after I interrupt username completion or
|
||||
F3) Why does bash dump core after I interrupt username completion or
|
||||
`~user' tilde expansion on a machine running NIS?
|
||||
|
||||
This is a famous and long-standing bug in the SunOS YP (sorry, NIS)
|
||||
|
|
@ -1077,7 +1133,7 @@ times; that's probably why this has never been fixed. You can
|
|||
run configure with the `--without-gnu-malloc' option to use
|
||||
the C library malloc and avoid the problem.
|
||||
|
||||
35) I'm running SVR4.2. Why is the line erased every time I type `@'?
|
||||
F4) I'm running SVR4.2. Why is the line erased every time I type `@'?
|
||||
|
||||
The `@' character is the default `line kill' character in most
|
||||
versions of System V, including SVR4.2. You can change this
|
||||
|
|
@ -1088,7 +1144,7 @@ change the line kill character to control-u, type
|
|||
|
||||
where the `^' and `U' can be two separate characters.
|
||||
|
||||
36) Why does bash report syntax errors when my C News scripts use a
|
||||
F5) Why does bash report syntax errors when my C News scripts use a
|
||||
redirection before a subshell command?
|
||||
|
||||
The actual command in question is something like
|
||||
|
|
@ -1100,7 +1156,7 @@ is, in fact, a syntax error. Redirections may only precede `simple
|
|||
commands'. A subshell construct such as the above is one of the shell's
|
||||
`compound commands'. A redirection may only follow a compound command.
|
||||
|
||||
The file CWRU/sh-redir-hack in the bash-2.02 distribution is an
|
||||
The file CWRU/sh-redir-hack in the bash-2.03 distribution is an
|
||||
(unofficial) patch to parse.y that will modify the grammar to
|
||||
support this construct. It will not apply with `patch'; you must
|
||||
modify parse.y by hand. Note that if you apply this, you must
|
||||
|
|
@ -1109,7 +1165,7 @@ number of reduce/reduce conflicts into the shell grammar.
|
|||
|
||||
Section G: Where do I go from here?
|
||||
|
||||
37) How do I report bugs in bash, and where should I look for fixes and
|
||||
G1) How do I report bugs in bash, and where should I look for fixes and
|
||||
advice?
|
||||
|
||||
Use the `bashbug' script to report bugs. It is built and
|
||||
|
|
@ -1117,7 +1173,7 @@ installed at the same time as bash. It provides a standard
|
|||
template for reporting a problem and automatically includes
|
||||
information about your configuration and build environment.
|
||||
|
||||
`bashbug' sends its reports to bug-bash@prep.ai.mit.edu, which
|
||||
`bashbug' sends its reports to bug-bash@gnu.org, which
|
||||
is a large mailing list gatewayed to the usenet newsgroup gnu.bash.bug.
|
||||
|
||||
Bug fixes, answers to questions, and announcements of new releases
|
||||
|
|
@ -1125,24 +1181,23 @@ are all posted to gnu.bash.bug. Discussions concerning bash features
|
|||
and problems also take place there.
|
||||
|
||||
To reach the bash maintainers directly, send mail to
|
||||
bash-maintainers@prep.ai.mit.edu.
|
||||
bash-maintainers@gnu.org.
|
||||
|
||||
38) What kind of bash documentation is there?
|
||||
G2) What kind of bash documentation is there?
|
||||
|
||||
First, look in the doc directory in the bash distribution. It should
|
||||
contain at least the following files:
|
||||
|
||||
bash.1 an extensive, thorough Unix-style manual page
|
||||
builtins.1 a manual page covering just bash builtin commands
|
||||
bashref.texi a reference manual in GNU info format
|
||||
bash.html an HTML version of the manual page
|
||||
bashref.html an HTML version of the reference manual
|
||||
bashref.texi a reference manual in GNU tex`info format
|
||||
bashref.info an info version of the reference manual
|
||||
FAQ this file
|
||||
article.ms text of an article written for The Linux Journal
|
||||
readline.3 a man page describing readline
|
||||
|
||||
Postscript files created from the above source are available in
|
||||
the documentation distribution.
|
||||
Postscript, HTML, and ASCII files created from the above source are
|
||||
available in the documentation distribution.
|
||||
|
||||
There is additional documentation available for anonymous FTP from host
|
||||
ftp.cwru.edu in the `pub/bash' directory.
|
||||
|
|
@ -1158,14 +1213,14 @@ A second edition of this book is available, published in January, 1998.
|
|||
The ISBN number is 1-56592-347-2. Look for it in the same fine bookstores
|
||||
or on the web.
|
||||
|
||||
39) What's coming in future versions?
|
||||
G3) What's coming in future versions?
|
||||
|
||||
These are features I plan to include in a future version of bash.
|
||||
|
||||
a bash debugger (a minimally-tested version is included with bash-2.02)
|
||||
Programmable completion a la zsh
|
||||
Programmable completion a la zsh/tcsh
|
||||
|
||||
40) What's on the bash `wish list' for future versions?
|
||||
G4) What's on the bash `wish list' for future versions?
|
||||
|
||||
These are features that may or may not appear in a future version of bash.
|
||||
|
||||
|
|
@ -1177,14 +1232,17 @@ timeouts for the `read' builtin
|
|||
the ksh-93 ${!prefix*} and ${!prefix@} operators
|
||||
arithmetic ++ and -- prefix and postfix operators
|
||||
date-stamped command history
|
||||
a way to bind readline editing key sequences to shell commands
|
||||
a mechanism to open network connections and assign them to file descriptors
|
||||
using redirection (like ksh /dev/{tcp,udp})
|
||||
|
||||
41) When will the next release appear?
|
||||
G5) When will the next release appear?
|
||||
|
||||
The next version will appear sometime in 1998. Never make
|
||||
The next version will appear sometime in 1999. Never make
|
||||
predictions.
|
||||
|
||||
|
||||
This document is Copyright 1995, 1996, 1998 by Chester Ramey.
|
||||
This document is Copyright 1995-1999 by Chester Ramey.
|
||||
|
||||
Permission is hereby granted, without written agreement and
|
||||
without license or royalty fees, to use, copy, and distribute
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue