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Emit zero-width bash prompt sequence from external binary
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In bash, how do I encode zero-width sequences into PS1, when those sequences are coming from stdout of an external process or function? How do I implement writes-prompt-sequences-to-stdout so that it can emit multi-colored text to the prompt?
PS1='$( writes-prompt-sequences-to-stdout )'
I know that, when writing a bash PS1 prompt, I must wrap zero-width sequences in [ ] so bash can compute correct prompt width.
PS1='[e[0;35m]$ [e[00m]' bash does not print the [ ] and understands the prompt is only 2 characters wide.
How do I move those sequences into an external function? The following does not work, my prompt looks like []$ [], even though I can run render-prompt and see it writing the correct sequence of bytes to stdout.
PS1='$( render-prompt )'
function render-prompt {
printf '[e[0;35m]$ [e[00m]'
}
Moving the printf call into PS1 does work:
PS1='$( printf '"'"'[e[0;35m]$ [e[00m]'"'"' )'
I theorized, perhaps bash is scanning the PS1 string before execution to count the number of zero-width bytes. So I tried tricking it by encoding [] sequences that aren't printed, but it correctly ignores the trick.
PS1='$( printf '"'"'$$$$$'"'"' '"'"'[e[00m]'"'"' )'
My question:
How do I write [ ] sequences to stdout from a function or binary that is invoked via PS1?
bash prompt
edited 2 hours ago
Jeff Schaller
42.9k1159137
asked 3 hours ago
cspotcodecspotcode
1462
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cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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add a comment |
In bash, how do I encode zero-width sequences into PS1, when those sequences are coming from stdout of an external process or function? How do I implement writes-prompt-sequences-to-stdout so that it can emit multi-colored text to the prompt?
PS1='$( writes-prompt-sequences-to-stdout )'
I know that, when writing a bash PS1 prompt, I must wrap zero-width sequences in [ ] so bash can compute correct prompt width.
PS1='[e[0;35m]$ [e[00m]' bash does not print the [ ] and understands the prompt is only 2 characters wide.
How do I move those sequences into an external function? The following does not work, my prompt looks like []$ [], even though I can run render-prompt and see it writing the correct sequence of bytes to stdout.
PS1='$( render-prompt )'
function render-prompt {
printf '[e[0;35m]$ [e[00m]'
}
Moving the printf call into PS1 does work:
PS1='$( printf '"'"'[e[0;35m]$ [e[00m]'"'"' )'
I theorized, perhaps bash is scanning the PS1 string before execution to count the number of zero-width bytes. So I tried tricking it by encoding [] sequences that aren't printed, but it correctly ignores the trick.
PS1='$( printf '"'"'$$$$$'"'"' '"'"'[e[00m]'"'"' )'
My question:
How do I write [ ] sequences to stdout from a function or binary that is invoked via PS1?
bash prompt
edited 2 hours ago
Jeff Schaller
42.9k1159137
asked 3 hours ago
cspotcodecspotcode
1462
New contributor
cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
In bash, how do I encode zero-width sequences into PS1, when those sequences are coming from stdout of an external process or function? How do I implement writes-prompt-sequences-to-stdout so that it can emit multi-colored text to the prompt?
PS1='$( writes-prompt-sequences-to-stdout )'
I know that, when writing a bash PS1 prompt, I must wrap zero-width sequences in [ ] so bash can compute correct prompt width.
PS1='[e[0;35m]$ [e[00m]' bash does not print the [ ] and understands the prompt is only 2 characters wide.
How do I move those sequences into an external function? The following does not work, my prompt looks like []$ [], even though I can run render-prompt and see it writing the correct sequence of bytes to stdout.
PS1='$( render-prompt )'
function render-prompt {
printf '[e[0;35m]$ [e[00m]'
}
Moving the printf call into PS1 does work:
PS1='$( printf '"'"'[e[0;35m]$ [e[00m]'"'"' )'
I theorized, perhaps bash is scanning the PS1 string before execution to count the number of zero-width bytes. So I tried tricking it by encoding [] sequences that aren't printed, but it correctly ignores the trick.
PS1='$( printf '"'"'$$$$$'"'"' '"'"'[e[00m]'"'"' )'
My question:
How do I write [ ] sequences to stdout from a function or binary that is invoked via PS1?
bash prompt
edited 2 hours ago
Jeff Schaller
42.9k1159137
asked 3 hours ago
cspotcodecspotcode
1462
New contributor
cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
In bash, how do I encode zero-width sequences into PS1, when those sequences are coming from stdout of an external process or function? How do I implement writes-prompt-sequences-to-stdout so that it can emit multi-colored text to the prompt?
PS1='$( writes-prompt-sequences-to-stdout )'
I know that, when writing a bash PS1 prompt, I must wrap zero-width sequences in [ ] so bash can compute correct prompt width.
PS1='[e[0;35m]$ [e[00m]' bash does not print the [ ] and understands the prompt is only 2 characters wide.
How do I move those sequences into an external function? The following does not work, my prompt looks like []$ [], even though I can run render-prompt and see it writing the correct sequence of bytes to stdout.
PS1='$( render-prompt )'
function render-prompt {
printf '[e[0;35m]$ [e[00m]'
}
Moving the printf call into PS1 does work:
PS1='$( printf '"'"'[e[0;35m]$ [e[00m]'"'"' )'
I theorized, perhaps bash is scanning the PS1 string before execution to count the number of zero-width bytes. So I tried tricking it by encoding [] sequences that aren't printed, but it correctly ignores the trick.
PS1='$( printf '"'"'$$$$$'"'"' '"'"'[e[00m]'"'"' )'
My question:
How do I write [ ] sequences to stdout from a function or binary that is invoked via PS1?
bash prompt
bash prompt
edited 2 hours ago
Jeff Schaller
42.9k1159137
asked 3 hours ago
cspotcodecspotcode
1462
New contributor
cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 2 hours ago
Jeff Schaller
42.9k1159137
asked 3 hours ago
cspotcodecspotcode
1462
New contributor
cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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edited 2 hours ago
Jeff Schaller
42.9k1159137
edited 2 hours ago
Jeff Schaller
42.9k1159137
edited 2 hours ago
Jeff Schaller
42.9k1159137
42.9k1159137
asked 3 hours ago
cspotcodecspotcode
1462
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cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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asked 3 hours ago
cspotcodecspotcode
1462
asked 3 hours ago
cspotcodecspotcode
1462
1462
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cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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I figured it out. Bash special-cases e, [, and ] within PS1. It coverts e to an escape byte, [ to a 1 byte, and ] to a 2 byte. External commands must write 1 and 2 bytes to stdout.
According to ASCII, these encode "start of heading" and "start of text."
http://www.columbia.edu/kermit/ascii.html
Here's a working example, which relies on printf converting escapes within the first positional parameter into the correct bytes:
PS1='$( render-prompt )'
function render-prompt {
printf '133[0;35m2$ 133[00m2'
}
render-prompt | hexdump -C
00000000 01 1b 5b 30 3b 33 35 6d 02 24 20 01 1b 5b 30 30 |..[0;35m.$ ..[00|
00000010 6d 02 |m.|
00000012
answered 3 hours ago
cspotcodecspotcode
1462
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cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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You correctly figured out the 1, 2 and e. But there's a better and more correct way to produce the sequences.
The printf command takes FORMAT as the first argument. This format consumes the subsequent arguments. So your function could be better written this way:
render-prompt () { printf "1%b2%s1%b2" 'e[0;35m' '$ ' 'e[00m'; }
The first argument is "1%b2%s1%b2" and this is the format. It's a good and logical place for 1 and 2, which embrace the %b parameters. (The %bs are -escaped strings and %s represents a standard string.)
The others are 'e[0;35m', '$ ' and 'e[00m', which correspond to %b, %s and %b in the format. Here I'd put es, as they escape the [ braces they precede.
answered 46 mins ago
TomaszTomasz
9,94952966
add a comment |
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2 Answers
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I figured it out. Bash special-cases e, [, and ] within PS1. It coverts e to an escape byte, [ to a 1 byte, and ] to a 2 byte. External commands must write 1 and 2 bytes to stdout.
According to ASCII, these encode "start of heading" and "start of text."
http://www.columbia.edu/kermit/ascii.html
Here's a working example, which relies on printf converting escapes within the first positional parameter into the correct bytes:
PS1='$( render-prompt )'
function render-prompt {
printf '133[0;35m2$ 133[00m2'
}
render-prompt | hexdump -C
00000000 01 1b 5b 30 3b 33 35 6d 02 24 20 01 1b 5b 30 30 |..[0;35m.$ ..[00|
00000010 6d 02 |m.|
00000012
answered 3 hours ago
cspotcodecspotcode
1462
New contributor
cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
I figured it out. Bash special-cases e, [, and ] within PS1. It coverts e to an escape byte, [ to a 1 byte, and ] to a 2 byte. External commands must write 1 and 2 bytes to stdout.
According to ASCII, these encode "start of heading" and "start of text."
http://www.columbia.edu/kermit/ascii.html
Here's a working example, which relies on printf converting escapes within the first positional parameter into the correct bytes:
PS1='$( render-prompt )'
function render-prompt {
printf '133[0;35m2$ 133[00m2'
}
render-prompt | hexdump -C
00000000 01 1b 5b 30 3b 33 35 6d 02 24 20 01 1b 5b 30 30 |..[0;35m.$ ..[00|
00000010 6d 02 |m.|
00000012
answered 3 hours ago
cspotcodecspotcode
1462
New contributor
cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
I figured it out. Bash special-cases e, [, and ] within PS1. It coverts e to an escape byte, [ to a 1 byte, and ] to a 2 byte. External commands must write 1 and 2 bytes to stdout.
According to ASCII, these encode "start of heading" and "start of text."
http://www.columbia.edu/kermit/ascii.html
Here's a working example, which relies on printf converting escapes within the first positional parameter into the correct bytes:
PS1='$( render-prompt )'
function render-prompt {
printf '133[0;35m2$ 133[00m2'
}
render-prompt | hexdump -C
00000000 01 1b 5b 30 3b 33 35 6d 02 24 20 01 1b 5b 30 30 |..[0;35m.$ ..[00|
00000010 6d 02 |m.|
00000012
answered 3 hours ago
cspotcodecspotcode
1462
New contributor
cspotcode is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I figured it out. Bash special-cases e, [, and ] within PS1. It coverts e to an escape byte, [ to a 1 byte, and ] to a 2 byte. External commands must write 1 and 2 bytes to stdout.
According to ASCII, these encode "start of heading" and "start of text."
http://www.columbia.edu/kermit/ascii.html
Here's a working example, which relies on printf converting escapes within the first positional parameter into the correct bytes:
PS1='$( render-prompt )'
function render-prompt {
printf '133[0;35m2$ 133[00m2'
}
render-prompt | hexdump -C
00000000 01 1b 5b 30 3b 33 35 6d 02 24 20 01 1b 5b 30 30 |..[0;35m.$ ..[00|
00000010 6d 02 |m.|
00000012
answered 3 hours ago
cspotcodecspotcode
1462
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answered 3 hours ago
cspotcodecspotcode
1462
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answered 3 hours ago
cspotcodecspotcode
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answered 3 hours ago
cspotcodecspotcode
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You correctly figured out the 1, 2 and e. But there's a better and more correct way to produce the sequences.
The printf command takes FORMAT as the first argument. This format consumes the subsequent arguments. So your function could be better written this way:
render-prompt () { printf "1%b2%s1%b2" 'e[0;35m' '$ ' 'e[00m'; }
The first argument is "1%b2%s1%b2" and this is the format. It's a good and logical place for 1 and 2, which embrace the %b parameters. (The %bs are -escaped strings and %s represents a standard string.)
The others are 'e[0;35m', '$ ' and 'e[00m', which correspond to %b, %s and %b in the format. Here I'd put es, as they escape the [ braces they precede.
answered 46 mins ago
TomaszTomasz
9,94952966
add a comment |
You correctly figured out the 1, 2 and e. But there's a better and more correct way to produce the sequences.
The printf command takes FORMAT as the first argument. This format consumes the subsequent arguments. So your function could be better written this way:
render-prompt () { printf "1%b2%s1%b2" 'e[0;35m' '$ ' 'e[00m'; }
The first argument is "1%b2%s1%b2" and this is the format. It's a good and logical place for 1 and 2, which embrace the %b parameters. (The %bs are -escaped strings and %s represents a standard string.)
The others are 'e[0;35m', '$ ' and 'e[00m', which correspond to %b, %s and %b in the format. Here I'd put es, as they escape the [ braces they precede.
answered 46 mins ago
TomaszTomasz
9,94952966
add a comment |
You correctly figured out the 1, 2 and e. But there's a better and more correct way to produce the sequences.
The printf command takes FORMAT as the first argument. This format consumes the subsequent arguments. So your function could be better written this way:
render-prompt () { printf "1%b2%s1%b2" 'e[0;35m' '$ ' 'e[00m'; }
The first argument is "1%b2%s1%b2" and this is the format. It's a good and logical place for 1 and 2, which embrace the %b parameters. (The %bs are -escaped strings and %s represents a standard string.)
The others are 'e[0;35m', '$ ' and 'e[00m', which correspond to %b, %s and %b in the format. Here I'd put es, as they escape the [ braces they precede.
answered 46 mins ago
TomaszTomasz
9,94952966
You correctly figured out the 1, 2 and e. But there's a better and more correct way to produce the sequences.
The printf command takes FORMAT as the first argument. This format consumes the subsequent arguments. So your function could be better written this way:
render-prompt () { printf "1%b2%s1%b2" 'e[0;35m' '$ ' 'e[00m'; }
The first argument is "1%b2%s1%b2" and this is the format. It's a good and logical place for 1 and 2, which embrace the %b parameters. (The %bs are -escaped strings and %s represents a standard string.)
The others are 'e[0;35m', '$ ' and 'e[00m', which correspond to %b, %s and %b in the format. Here I'd put es, as they escape the [ braces they precede.
answered 46 mins ago
TomaszTomasz
9,94952966
answered 46 mins ago
TomaszTomasz
9,94952966
answered 46 mins ago
TomaszTomasz
9,94952966
answered 46 mins ago
TomaszTomasz
9,94952966
9,94952966
add a comment |
add a comment |
cspotcode is a new contributor. Be nice, and check out our Code of Conduct.
cspotcode is a new contributor. Be nice, and check out our Code of Conduct.
cspotcode is a new contributor. Be nice, and check out our Code of Conduct.
cspotcode is a new contributor. Be nice, and check out our Code of Conduct.
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