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Implement the "pipefail" option (same semantics as in other shells)

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to cause (when set, which it is not by default) the exit status of a
pipe to be 0 iff all commands in the pipe exited with status 0, and
otherwise, the status of the rightmost command to exit with a non-0
status.

In the doc, while describing this, also reword some of the text about
commands in general, how they are structured, and when they are executed.
This commit is contained in:
kre 2017-07-24 14:17:11 +00:00
parent 59695ae2d7
commit ed2c7aaa15
3 changed files with 133 additions and 57 deletions
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24
bin/sh/jobs.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: jobs.c,v 1.87 2017/06/17 12:12:50 kre Exp $ */
/* $NetBSD: jobs.c,v 1.88 2017/07/24 14:17:11 kre Exp $ */
/*-
* Copyright (c) 1991, 1993
@ -37,7 +37,7 @@
#if 0
static char sccsid[] = "@(#)jobs.c 8.5 (Berkeley) 5/4/95";
#else
__RCSID("$NetBSD: jobs.c,v 1.87 2017/06/17 12:12:50 kre Exp $");
__RCSID("$NetBSD: jobs.c,v 1.88 2017/07/24 14:17:11 kre Exp $");
#endif
#endif /* not lint */
@ -649,7 +649,17 @@ waitcmd(int argc, char **argv)
if (dowait(WBLOCK|WNOFREE, job) == -1)
return 128 + lastsig();
}
status = job->ps[job->nprocs ? job->nprocs - 1 : 0].status;
if (pipefail && job->nprocs) {
int i;
status = 0;
for (i = 0; i < job->nprocs; i++)
if (job->ps[i].status != 0)
status = job->ps[i].status;
} else
status =
job->ps[job->nprocs ? job->nprocs - 1 : 0].status;
if (WIFEXITED(status))
retval = WEXITSTATUS(status);
#if JOBS
@ -1013,7 +1023,13 @@ waitforjob(struct job *jp)
if (jp->state == JOBSTOPPED && curjob != jp - jobtab)
set_curjob(jp, 2);
#endif
status = jp->ps[jp->nprocs - 1].status;
if (pipefail) {
status = 0;
for (st = 0; st < jp->nprocs; st++)
if (jp->ps[st].status != 0)
status = jp->ps[st].status;
} else
status = jp->ps[jp->nprocs - 1].status;
/* convert to 8 bits */
if (WIFEXITED(status))
st = WEXITSTATUS(status);

3
bin/sh/option.list
View File

@ -1,4 +1,4 @@
/* $NetBSD: option.list,v 1.5 2017/06/30 23:02:56 kre Exp $ */
/* $NetBSD: option.list,v 1.6 2017/07/24 14:17:11 kre Exp $ */
/*
* define the shell's settable options
@ -65,6 +65,7 @@ posix posix # be closer to POSIX compat
qflag quietprofile q # disable -v/-x in startup files
fnline1 local_lineno L on # number lines in funcs starting at 1
promptcmds promptcmds # allow $( ) in PS1 (et al).
pipefail pipefail # pipe exit status
// editline/history related options ("vi" is standard, 'V' and others are not)
// only one of vi/emacs can be set, hence the "set" definition, value

163
bin/sh/sh.1
View File

@ -1,4 +1,4 @@
.\" $NetBSD: sh.1,v 1.161 2017/07/24 13:21:14 kre Exp $
.\" $NetBSD: sh.1,v 1.162 2017/07/24 14:17:11 kre Exp $
.\" Copyright (c) 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
@ -453,6 +453,12 @@ in the
.Sx Built-ins
section.)
(Not implemented.)
.It "\ \ " Em pipefail
If set, the way the exit status of a pipeline is determined
is altered.
See
.Sx Pipelines
below for the details.
.It "\ \ " Em posix
Enables closer adherence to the POSIX shell standard.
This option will default set at shell startup if the
@ -822,22 +828,26 @@ is returned.
.Ss Complex Commands
Complex commands are combinations of simple commands with control
operators or reserved words, together creating a larger complex command.
More generally, a command is one of the following:
.Bl -bullet
.It
simple command
.It
pipeline
.It
list or compound-list
.It
compound command
.It
function definition
Overall, a shell program is a:
.Bl -tag -width XpipelineX
.It list
Which is a sequence of one or more AND-OR lists.
.It "AND-OR list"
is a sequence of one or more pipelines.
.It pipeline
is a sequence of one or more commands.
.It command
is one of a simple command, a compound command, or a function definition.
.It "simple command"
has been explained above, and is the basic building block.
.It "compound command"
provides mechanisms to group lists to achieve different effects.
.It "function definition"
allows new simple commands to be created as groupings of existing commands.
.El
.Pp
Unless otherwise stated, the exit status of a command is that of the last
simple command executed by the command.
Unless otherwise stated, the exit status of a list
is that of the last simple command executed by the list.
.Ss Pipelines
A pipeline is a sequence of one or more commands separated
by the control operator
@ -845,11 +855,23 @@ by the control operator
and optionally preceded by the
.Dq \&!
reserved word.
Note that
.Sq \&|
is an operator, and so is recognized anywhere it appears unquoted,
it does not require surrounding white space or other syntax elements.
On the other hand
.Dq \&!
being a reserved word, must be separated from adjacent words by
white space (or other operators, perhaps redirects) and is only
recognized as the reserved word when it appears in a command word
position (such as at the beginning of a pipeline.)
.Pp
The standard output of all but
the last command is connected to the standard input
the last command in the sequence is connected to the standard input
of the next command.
The standard output of the last
command is inherited from the shell, as usual.
command is inherited from the shell, as usual,
as is the standard input of the first command.
.Pp
The format for a pipeline is:
.Pp
@ -857,20 +879,36 @@ The format for a pipeline is:
.Pp
The standard output of command1 is connected to the standard input of
command2.
The standard input, standard output, or both of a command is
The standard input, standard output, or both of each command is
considered to be assigned by the pipeline before any redirection specified
by redirection operators that are part of the command are performed.
.Pp
If the pipeline is not in the background (discussed later), the shell
waits for all commands to complete.
.Pp
If the reserved word ! does not precede the pipeline, the exit status is
the exit status of the last command specified in the pipeline.
Otherwise, the exit status is the logical NOT of the exit status of the
last command.
That is, if the last command returns zero, the exit status
is 1; if the last command returns greater than zero, the exit status is
zero.
The commands in a pipeline can either be simple commands,
or one of the compound commands described below.
The simplest case of a pipeline is a single simple command.
.Pp
If the
.Ic pipefail
option is set when the pipeline completes and its status is
collected, the pipeline status is the status of
the last (rightmost) command in the pipeline to exit with non-zero exit
status, or zero, if, and only if, all commands in the pipeline
exited with a status of zero.
If the
.Ic pipefail
option is not set, which is the default state,
the pipeline status is the exit
status of the last command in the pipeline,
and the exit status of any other commands in the pipeline is ignored.
.Pp
If the reserved word ! precedes the pipeline, the exit status
becomes the logical NOT of the pipeline status as determined above.
That is, if the pipeline status is zero, the exit status is 1;
if the pipeline status is other than zero, the exit status is zero.
If there is no ! reserved word, the pipeline status becomes the exit status.
.Pp
Because pipeline assignment of standard input or standard output or both
takes place before redirection, it can be modified by redirection.
@ -881,24 +919,29 @@ For example:
sends both the standard output and standard error of command1
to the standard input of command2.
.Pp
Note that unlike some other shells, each process in the pipeline is a
child of the invoking shell (unless it is a shell built-in, in which case
it executes in the current shell -- but any effect it has on the
environment is wiped).
.Pp
A pipeline is a simple case of an AND-OR-list (described below.)
A ; or
.Aq newline
terminator causes the preceding AND-OR-list (described
next) to be executed sequentially; a & causes asynchronous execution of
the preceding AND-OR-list.
terminator causes the preceding pipeline, or more generally,
the preceding AND-OR-list to be executed sequentially;
that is, the shell executes the commands, and waits for them
to finish before proceeding to following commands.
An & terminator causes asynchronous (background) execution
of the preceding AND-OR-list (see the next paragraph below).
The exit status of an asynchronous AND-OR-list is zero.
The actual status of the commands,
after they have completed,
can be obtained using the
.Ic wait
built-in command described later.
.Pp
Note that unlike some other shells, each process in the pipeline is a
child of the invoking shell (unless it is a shell built-in, in which case
it executes in the current shell -- but any effect it has on the
environment is wiped).
.Ss Background Commands -- &
If a command is terminated by the control operator ampersand (&), the
If a command, pipeline, or AND-OR-list
is terminated by the control operator ampersand (&), the
shell executes the command asynchronously -- that is, the shell does not
wait for the command to finish before executing the next command.
.Pp
@ -913,11 +956,19 @@ The process identifier of the most recent command started in the
background can be obtained from the value of the special parameter
.Dq \&!
(see
.Sx Special Parameters ) .
.Sx Special Parameters )
provided it is accessed before the next asynchronous command is started.
.Ss Lists -- Generally Speaking
A list is a sequence of one or more commands separated by newlines,
semicolons, or ampersands, and optionally terminated by one of these three
characters.
A shell program, which includes the commands given to an
interactive shell, is a list.
Each command in such a list is executed when it is fully parsed.
Another use of a list is as a complete-command,
which is parsed in its entirety, and then later the commands in
the list are executed only if there were no parsing errors.
.Pp
The commands in a list are executed in the order they are written.
If command is followed by an ampersand, the shell starts the
command and immediately proceeds to the next command; otherwise it waits
@ -927,28 +978,32 @@ A newline is equivalent to a
when no other operator is present, and the command being input
could syntactically correctly be terminated at the point where
the newline is encountered, otherwise it is just whitespace.
.Ss Short-Circuit List Operators
.Ss AND-OR Lists (Short-Circuit List Operators)
.Dq &&
and
.Dq ||
are AND-OR list operators.
After executing the commands that precede the
.Dq &&
executes the first command, and then executes the second command if and only
if the exit status of the first command is zero.
the subsequent command is executed
if and only if the exit status of the preceding command(s) is zero.
.Dq ||
is similar, but executes the second command if and only if the exit status
of the first command is nonzero.
is similar, but executes the subsequent command if and only if the exit status
of the preceding command is nonzero.
If a command is not executed, the exit status remains unchanged
and the following AND-OR list operator (if any) uses that status.
.Dq &&
and
.Dq ||
both have the same priority.
Note that these operators are left-associative, so
.Dq true || echo bar && echo baz
.Dl true || echo bar && echo baz
writes
.Dq baz
and nothing else.
This is not the way it works in C.
.Ss Flow-Control Constructs -- if, while, for, case
.Ss Flow-Control Constructs -- if, while, until, for, case
These commands are instances of compound commands.
The syntax of the
.Ic if
command is
@ -1002,9 +1057,15 @@ do list
done
.Ed
.Pp
The words are expanded, or "$@" if no words are given,
The words are expanded, or "$@" if
.Dq in
(and the following words) is not present,
and then the list is executed repeatedly with the
variable set to each word in turn.
If
.Dq in
appears after the variable, but no words are
present, the list is not executed, and the exit status is zero.
.Ic do
and
.Ic done
@ -1040,7 +1101,7 @@ innermost
or
.Ic until
loops, and then continues with the next iteration of the enclosing loop.
These are implemented as built-in commands.
These are implemented as special built-in commands.
The parameter
.Ar num ,
if given, must be an unsigned positive integer (greater than zero).
@ -1051,8 +1112,8 @@ The syntax of the
command is
.Bd -literal -offset indent
case word in
[(] pattern ) list ;&
[(] pattern ) list ;;
[(] pattern ) [ list ] ;&
[(] pattern ) [ list ] ;;
\&...
esac
.Ed
@ -1067,8 +1128,8 @@ Word is expanded and matched against each pattern in turn,
from first to last,
with each pattern being expanded just before the match is attempted.
When a match is found, pattern comparisons cease, and the associated
.Dq list
(which may be empty)
.Dq list ,
if given,
is evaluated.
If the list is terminated with
.Dq \&;&
@ -1078,19 +1139,17 @@ When a list terminated with
.Dq \&;;
has been executed, or when
.Ic esac
is reached execution of the
is reached, execution of the
.Ic case
statement is complete.
The exit status is that of the last command executed
from the last list evaluated, if any, or zero otherwise.
.Ss Grouping Commands Together
Commands may be grouped by writing either
.Pp
.Dl (list)
.Pp
or
.Pp
.Dl { list; }
These also form compound commands.
.Pp
Note that while parentheses are operators, and do not require
any extra syntax, braces are reserved words, so the opening brace