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Kurtis Rader
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return to psub --file being the default
The recent change to switch `psub` to use `argparse` caused it to use a fifo by default because it inadvertently fixed a long standing bug in the fish script. This changes the behavior back to `psub --file` being the default behavior and introduces a `--fifo` flag. It also updates the documentation to make it clearer when and why `--fifo` mode should not be used. Fixes #4222
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‎doc_src/psub.txt‎

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@@ -2,24 +2,27 @@
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\subsection psub-synopsis Synopsis
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\fish{synopsis}
5-
COMMAND1 ( COMMAND2 | psub [-f] [-s SUFFIX])
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COMMAND1 ( COMMAND2 | psub [-F | --fifo] [-f | --file] [-s SUFFIX])
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\endfish
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\subsection psub-description Description
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10-
Posix shells feature a syntax that is a mix between command substitution and piping, called process substitution. It is used to send the output of a command into the calling command, much like command substitution, but with the difference that the output is not sent through commandline arguments but through a named pipe, with the filename of the named pipe sent as an argument to the calling program. `psub` combined with a regular command substitution provides the same functionality.
10+
Some shells (e.g., ksh, bash) feature a syntax that is a mix between command substitution and piping, called process substitution. It is used to send the output of a command into the calling command, much like command substitution, but with the difference that the output is not sent through commandline arguments but through a named pipe, with the filename of the named pipe sent as an argument to the calling program. `psub` combined with a regular command substitution provides the same functionality.
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12-
If the `-f` or `--file` switch is given to `psub`, `psub` will use a regular file instead of a named pipe to communicate with the calling process. This will cause `psub` to be significantly slower when large amounts of data are involved, but has the advantage that the reading process can seek in the stream.
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The following options are available:
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14-
If the `-s` or `---suffix` switch is given, `psub` will append SUFFIX to the filename.
14+
- `-f` or `--file` will cause psub to use a regular file instead of a named pipe to communicate with the calling process. This will cause `psub` to be significantly slower when large amounts of data are involved, but has the advantage that the reading process can seek in the stream. This is the default.
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- `-F` or `--fifo` will cause psub to use a named pipe rather than a file. You should only use this if the command produces no more than 8 KiB of output. The limit on the amount of data a FIFO can buffer varies with the OS but is typically 8 KiB, 16 KiB or 64 KiB. If you use this option and the command on the left of the psub pipeline produces more output a deadlock is likely to occur.
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- `-s` or `--suffix` will append SUFFIX to the filename.
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\subsection psub-example Example
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\fish
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diff (sort a.txt | psub) (sort b.txt | psub)
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# shows the difference between the sorted versions of files `a.txt` and `b.txt`.
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23-
source-highlight -f esc (cpp main.c | psub -s .c)
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source-highlight -f esc (cpp main.c | psub -f -s .c)
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# highlights `main.c` after preprocessing as a C source.
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\endfish

‎share/functions/psub.fish‎

Lines changed: 10 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
function psub --description "Read from stdin into a file and output the filename. Remove the file when the command that called psub exits."
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set -l options 'h/help' 'f/file' 's/suffix='
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set -l options -x 'f,F' -x 'F,s' 'h/help' 'f/file' 'F/fifo' 's/suffix=' 'T-testing'
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argparse -n psub --max-args=0 $options -- $argv
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or return
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@@ -21,10 +21,10 @@ function psub --description "Read from stdin into a file and output the filename
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set -q TMPDIR
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and set tmpdir $TMPDIR
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if not set -q _flag_file
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if set -q _flag_fifo
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# Write output to pipe. This needs to be done in the background so
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# that the command substitution exits without needing to wait for
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# all the commands to exit
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# all the commands to exit.
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set dirname (mktemp -d $tmpdir/.psub.XXXXXXXXXX)
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or return
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set filename $dirname/psub.fifo"$_flag_suffix"
@@ -35,13 +35,18 @@ function psub --description "Read from stdin into a file and output the filename
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cat >$filename
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else
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set dirname (mktemp -d $tmpdir/.psub.XXXXXXXXXX)
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set filename $dirname/psub"$_flag_suffix"
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set filename "$dirname/psub$_flag_suffix"
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cat >$filename
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end
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# Write filename to stdout
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echo $filename
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45+
# This flag isn't documented. It's strictly for our unit tests.
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if set -q _flag_testing
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return
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end
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# Find unique function name
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while true
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set funcname __fish_psub_(random)
@@ -53,7 +58,7 @@ function psub --description "Read from stdin into a file and output the filename
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# Make sure we erase file when caller exits
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function $funcname --on-job-exit caller --inherit-variable filename --inherit-variable dirname --inherit-variable funcname
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command rm $filename
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if count $dirname >/dev/null
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if test -n "$dirname"
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command rmdir $dirname
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end
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functions -e $funcname

‎tests/psub.err‎

Whitespace-only changes.

‎tests/psub.in‎

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# Test psub behavior
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set -l filename (echo foo | psub --testing)
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test -f $filename
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or echo 'psub is not a regular file' >&2
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rm $filename
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set -l filename (echo foo | psub --testing --file)
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test -f $filename
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or echo 'psub is not a regular file' >&2
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rm $filename
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set -l filename (echo foo | psub --testing --fifo)
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test -p $filename
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or echo 'psub is not a fifo' >&2
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rm $filename
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cat (echo foo | psub)
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cat (echo bar | psub --fifo)
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cat (echo baz | psub)
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set -l filename (echo foo | psub)
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if test -e $filename
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echo 'psub file was not deleted'
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else
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echo 'psub file was deleted'
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end
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# The --file flag is the default behavior.
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if count (echo foo | psub -s .cc | grep -o '\.cc$') >/dev/null
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echo 'psub filename ends with .cc'
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else
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echo 'psub filename does not end with .cc'
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end
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# Make sure we get the same result if we explicitly ask for a temp file.
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if count (echo foo | psub -f -s .cc | grep -o '\.cc$') >/dev/null
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echo 'psub filename ends with .cc'
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else
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echo 'psub filename does not end with .cc'
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end
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set -l filename (echo foo | psub -s .fish)
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if test -e (dirname $filename)
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echo 'psub directory was not deleted'
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else
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echo 'psub directory was deleted'
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end
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diff -q (__fish_print_help psub | psub) (psub -hs banana | psub)

‎tests/psub.out‎

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foo
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bar
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baz
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psub file was deleted
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psub filename ends with .cc
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psub filename ends with .cc
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psub directory was deleted

‎tests/test9.in‎

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@@ -7,7 +7,7 @@ cat ../test/temp/file_truncation_test.txt
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echo -n > ../test/temp/file_truncation_test.txt
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cat ../test/temp/file_truncation_test.txt
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10-
# Test events.
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# Test events.
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# This pattern caused a crash; github issue #449
@@ -85,39 +85,6 @@ eval 'status -n
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status -n
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status -n'
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88-
# Test psub
89-
cat (echo foo | psub)
90-
cat (echo bar | psub)
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cat (echo baz | psub)
92-
93-
set -l filename (echo foo | psub)
94-
if test -e $filename
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echo 'psub file was not deleted'
96-
else
97-
echo 'psub file was deleted'
98-
end
99-
100-
if count (echo foo | psub -s .cc | grep -o '\.cc$') >/dev/null
101-
echo 'psub filename ends with .cc'
102-
else
103-
echo 'psub filename does not end with .cc'
104-
end
105-
106-
if count (echo foo | psub -f -s .cc | grep -o '\.cc$') >/dev/null
107-
echo 'psub filename ends with .cc'
108-
else
109-
echo 'psub filename does not end with .cc'
110-
end
111-
112-
set -l filename (echo foo | psub -s .fish)
113-
if test -e (dirname $filename)
114-
echo 'psub directory was not deleted'
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else
116-
echo 'psub directory was deleted'
117-
end
118-
119-
diff -q (__fish_print_help psub | psub) (psub -hs banana | psub)
120-
12188
# Test support for unbalanced blocks
12289
function try_unbalanced_block
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../test/root/bin/fish -c "echo $argv | source " 2>&1 | grep "Missing end" 1>&2

‎tests/test9.out‎

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@@ -13,13 +13,6 @@ Testing for loop
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1
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foo
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bar
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baz
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psub file was deleted
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psub filename ends with .cc
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psub filename ends with .cc
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psub directory was deleted
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bom_test
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not#a#comment
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is

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