Why does wc <<<â€œ$stringâ€ show a one-byte-longer length than printf â€œ$stringâ€

Why does wc <<<â€œ$stringâ€ show a one-byte-longer length than printf â€œ$stringâ€ | wc?

up vote
11
down vote

favorite

Accidentially, I found out that wc counts differently depending on how it gets the input from bash:

$ s='hello'
$ wc -m <<<"$s"
6
$ wc -c <<<"$s"
6
$ printf '%s' "$s" | wc -m
5
$ printf '%s' "$s" | wc -c
5

Is this - IMHO confusing - behaviour documented somewhere? What does wc count here - is this an assumed newline?

edited Jan 31 at 5:59

asked Jan 30 at 12:26

rexkogitans

308110

3

You can always pipe to od -c to see exactly what you have.
â€“Â ThorbjÃ¸rn Ravn Andersen
Jan 30 at 17:19

Or, better, xxd -g1.
â€“Â Ruslan
Jan 30 at 18:27

1

I hope printf "$s" isn't your actual script... hopefully you meant printf "%s" "$s"
â€“Â Mehrdad
Jan 30 at 23:23

Since there were so many comments about printf, I edited my post to reflect best practice.
â€“Â rexkogitans
Jan 31 at 6:01

add a commentÂ |Â

up vote
11
down vote

favorite

Accidentially, I found out that wc counts differently depending on how it gets the input from bash:

$ s='hello'
$ wc -m <<<"$s"
6
$ wc -c <<<"$s"
6
$ printf '%s' "$s" | wc -m
5
$ printf '%s' "$s" | wc -c
5

Is this - IMHO confusing - behaviour documented somewhere? What does wc count here - is this an assumed newline?

edited Jan 31 at 5:59

asked Jan 30 at 12:26

rexkogitans

308110

3

You can always pipe to od -c to see exactly what you have.
â€“Â ThorbjÃ¸rn Ravn Andersen
Jan 30 at 17:19

Or, better, xxd -g1.
â€“Â Ruslan
Jan 30 at 18:27

1

I hope printf "$s" isn't your actual script... hopefully you meant printf "%s" "$s"
â€“Â Mehrdad
Jan 30 at 23:23

Since there were so many comments about printf, I edited my post to reflect best practice.
â€“Â rexkogitans
Jan 31 at 6:01

add a commentÂ |Â

up vote
11
down vote

favorite

Accidentially, I found out that wc counts differently depending on how it gets the input from bash:

$ s='hello'
$ wc -m <<<"$s"
6
$ wc -c <<<"$s"
6
$ printf '%s' "$s" | wc -m
5
$ printf '%s' "$s" | wc -c
5

Is this - IMHO confusing - behaviour documented somewhere? What does wc count here - is this an assumed newline?

edited Jan 31 at 5:59

asked Jan 30 at 12:26

rexkogitans

308110

Accidentially, I found out that wc counts differently depending on how it gets the input from bash:

$ s='hello'
$ wc -m <<<"$s"
6
$ wc -c <<<"$s"
6
$ printf '%s' "$s" | wc -m
5
$ printf '%s' "$s" | wc -c
5

Is this - IMHO confusing - behaviour documented somewhere? What does wc count here - is this an assumed newline?

edited Jan 31 at 5:59

asked Jan 30 at 12:26

rexkogitans

308110

edited Jan 31 at 5:59

asked Jan 30 at 12:26

rexkogitans

308110

asked Jan 30 at 12:26

rexkogitans

308110

asked Jan 30 at 12:26

rexkogitans

308110

3

You can always pipe to od -c to see exactly what you have.
â€“Â ThorbjÃ¸rn Ravn Andersen
Jan 30 at 17:19

Or, better, xxd -g1.
â€“Â Ruslan
Jan 30 at 18:27

1

I hope printf "$s" isn't your actual script... hopefully you meant printf "%s" "$s"
â€“Â Mehrdad
Jan 30 at 23:23

Since there were so many comments about printf, I edited my post to reflect best practice.
â€“Â rexkogitans
Jan 31 at 6:01

add a commentÂ |Â

3

You can always pipe to od -c to see exactly what you have.
â€“Â ThorbjÃ¸rn Ravn Andersen
Jan 30 at 17:19

Or, better, xxd -g1.
â€“Â Ruslan
Jan 30 at 18:27

1

I hope printf "$s" isn't your actual script... hopefully you meant printf "%s" "$s"
â€“Â Mehrdad
Jan 30 at 23:23

Since there were so many comments about printf, I edited my post to reflect best practice.
â€“Â rexkogitans
Jan 31 at 6:01

You can always pipe to od -c to see exactly what you have.
â€“Â ThorbjÃ¸rn Ravn Andersen
Jan 30 at 17:19

Or, better, xxd -g1.
â€“Â Ruslan
Jan 30 at 18:27

I hope printf "$s" isn't your actual script... hopefully you meant printf "%s" "$s"
â€“Â Mehrdad
Jan 30 at 23:23

Since there were so many comments about printf, I edited my post to reflect best practice.
â€“Â rexkogitans
Jan 31 at 6:01

add a commentÂ |Â

2 Answers
2

active

oldest

votes

up vote
38
down vote

accepted

The difference is caused by a newline added to the here string. See the Bash manual:

The result is supplied as a single string, with a newline appended, to the command on its standard input (or file descriptor n if n is specified).

wc is counting in the same way, but its input is different.

edited Jan 30 at 16:36

answered Jan 30 at 12:30

Stephen Kitt

142k22308370

7

If should be noted that to print the (arbitrary) content of a variable without an added newline character, it should be printf %s "$var" (or print -rn -- "$var" with ksh-like shells), not printf "$var" which wouldn't work correctly for values of $var that contain % or backslash characters (or start with - with most implementations).
â€“Â StÃ©phane Chazelas
Jan 30 at 16:54

Note that the original here-string implementation in the Unix port of rc did not add that newline character.
â€“Â StÃ©phane Chazelas
Jan 30 at 16:56

add a commentÂ |Â

up vote
26
down vote

It's a succeeding newline added by the here-string redirector:

$ s="hello"
$ hexdump -C <<<"$s"
00000000 68 65 6c 6c 6f 0a |hello.|
00000006
$ printf "$s" | hexdump -C
00000000 68 65 6c 6c 6f |hello|
00000005

edited Jan 30 at 12:41

ilkkachu

49.8k674137

answered Jan 30 at 12:31

Murphy

1,7471517

add a commentÂ |Â

Your Answer

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "106"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
convertImagesToLinks: false,
noModals: false,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);

);

draft saved

draft discarded

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f420655%2fwhy-does-wc-string-show-a-one-byte-longer-length-than-printf-string-w%23new-answer', 'question_page');

);

Post as a guest

Name

2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

up vote
38
down vote

accepted

The difference is caused by a newline added to the here string. See the Bash manual:

The result is supplied as a single string, with a newline appended, to the command on its standard input (or file descriptor n if n is specified).

wc is counting in the same way, but its input is different.

edited Jan 30 at 16:36

answered Jan 30 at 12:30

Stephen Kitt

142k22308370

7

If should be noted that to print the (arbitrary) content of a variable without an added newline character, it should be printf %s "$var" (or print -rn -- "$var" with ksh-like shells), not printf "$var" which wouldn't work correctly for values of $var that contain % or backslash characters (or start with - with most implementations).
â€“Â StÃ©phane Chazelas
Jan 30 at 16:54

Note that the original here-string implementation in the Unix port of rc did not add that newline character.
â€“Â StÃ©phane Chazelas
Jan 30 at 16:56

add a commentÂ |Â

up vote
38
down vote

accepted

The difference is caused by a newline added to the here string. See the Bash manual:

The result is supplied as a single string, with a newline appended, to the command on its standard input (or file descriptor n if n is specified).

wc is counting in the same way, but its input is different.

edited Jan 30 at 16:36

answered Jan 30 at 12:30

Stephen Kitt

142k22308370

7

If should be noted that to print the (arbitrary) content of a variable without an added newline character, it should be printf %s "$var" (or print -rn -- "$var" with ksh-like shells), not printf "$var" which wouldn't work correctly for values of $var that contain % or backslash characters (or start with - with most implementations).
â€“Â StÃ©phane Chazelas
Jan 30 at 16:54

Note that the original here-string implementation in the Unix port of rc did not add that newline character.
â€“Â StÃ©phane Chazelas
Jan 30 at 16:56

add a commentÂ |Â

up vote
38
down vote

accepted

The difference is caused by a newline added to the here string. See the Bash manual:

The result is supplied as a single string, with a newline appended, to the command on its standard input (or file descriptor n if n is specified).

wc is counting in the same way, but its input is different.

edited Jan 30 at 16:36

answered Jan 30 at 12:30

Stephen Kitt

142k22308370

The difference is caused by a newline added to the here string. See the Bash manual:

The result is supplied as a single string, with a newline appended, to the command on its standard input (or file descriptor n if n is specified).

wc is counting in the same way, but its input is different.

edited Jan 30 at 16:36

answered Jan 30 at 12:30

Stephen Kitt

142k22308370

edited Jan 30 at 16:36

answered Jan 30 at 12:30

Stephen Kitt

142k22308370

answered Jan 30 at 12:30

Stephen Kitt

142k22308370

answered Jan 30 at 12:30

Stephen Kitt

142k22308370

7

If should be noted that to print the (arbitrary) content of a variable without an added newline character, it should be printf %s "$var" (or print -rn -- "$var" with ksh-like shells), not printf "$var" which wouldn't work correctly for values of $var that contain % or backslash characters (or start with - with most implementations).
â€“Â StÃ©phane Chazelas
Jan 30 at 16:54

Note that the original here-string implementation in the Unix port of rc did not add that newline character.
â€“Â StÃ©phane Chazelas
Jan 30 at 16:56

add a commentÂ |Â

7

If should be noted that to print the (arbitrary) content of a variable without an added newline character, it should be printf %s "$var" (or print -rn -- "$var" with ksh-like shells), not printf "$var" which wouldn't work correctly for values of $var that contain % or backslash characters (or start with - with most implementations).
â€“Â StÃ©phane Chazelas
Jan 30 at 16:54

Note that the original here-string implementation in the Unix port of rc did not add that newline character.
â€“Â StÃ©phane Chazelas
Jan 30 at 16:56

If should be noted that to print the (arbitrary) content of a variable without an added newline character, it should be printf %s "$var" (or print -rn -- "$var" with ksh-like shells), not printf "$var" which wouldn't work correctly for values of $var that contain % or backslash characters (or start with - with most implementations).
â€“Â StÃ©phane Chazelas
Jan 30 at 16:54

Note that the original here-string implementation in the Unix port of rc did not add that newline character.
â€“Â StÃ©phane Chazelas
Jan 30 at 16:56

add a commentÂ |Â

up vote
26
down vote

It's a succeeding newline added by the here-string redirector:

$ s="hello"
$ hexdump -C <<<"$s"
00000000 68 65 6c 6c 6f 0a |hello.|
00000006
$ printf "$s" | hexdump -C
00000000 68 65 6c 6c 6f |hello|
00000005

edited Jan 30 at 12:41

ilkkachu

49.8k674137

answered Jan 30 at 12:31

Murphy

1,7471517

add a commentÂ |Â

up vote
26
down vote

It's a succeeding newline added by the here-string redirector:

$ s="hello"
$ hexdump -C <<<"$s"
00000000 68 65 6c 6c 6f 0a |hello.|
00000006
$ printf "$s" | hexdump -C
00000000 68 65 6c 6c 6f |hello|
00000005

edited Jan 30 at 12:41

ilkkachu

49.8k674137

answered Jan 30 at 12:31

Murphy

1,7471517

add a commentÂ |Â

up vote
26
down vote

It's a succeeding newline added by the here-string redirector:

$ s="hello"
$ hexdump -C <<<"$s"
00000000 68 65 6c 6c 6f 0a |hello.|
00000006
$ printf "$s" | hexdump -C
00000000 68 65 6c 6c 6f |hello|
00000005

edited Jan 30 at 12:41

ilkkachu

49.8k674137

answered Jan 30 at 12:31

Murphy

1,7471517

It's a succeeding newline added by the here-string redirector:

$ s="hello"
$ hexdump -C <<<"$s"
00000000 68 65 6c 6c 6f 0a |hello.|
00000006
$ printf "$s" | hexdump -C
00000000 68 65 6c 6c 6f |hello|
00000005

edited Jan 30 at 12:41

ilkkachu

49.8k674137

answered Jan 30 at 12:31

Murphy

1,7471517

edited Jan 30 at 12:41

ilkkachu

49.8k674137

edited Jan 30 at 12:41

ilkkachu

49.8k674137

edited Jan 30 at 12:41

ilkkachu

49.8k674137

answered Jan 30 at 12:31

Murphy

1,7471517

answered Jan 30 at 12:31

Murphy

1,7471517

answered Jan 30 at 12:31

Murphy

1,7471517

add a commentÂ |Â

draft saved

draft discarded

draft saved

draft discarded

Post as a guest

Name

搜尋此網誌

mjhjmtu