Why does `printf “%s”` concatenate two following strings together? [duplicate]
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This question already has an answer here:
How does printf with multiple arguments separated by space work
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$ printf "%s" a b
ab$ printf "%s%s" a b
ab
I have some problem understand the format specifier for printf. If I am correct it is mostly the same as those for strings in the C programming language.
Why does the format specifier %s concatenate the two following strings together?
Why does %s not mean that there is only one string to substitute it, and ignore the remaining string?
Why are the results for two strings under %s and under %s%s the same?
bash printf
edited 2 days ago
Rui F Ribeiro
38.2k1475125
asked 2 days ago
Ben
2788
New contributor
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
marked as duplicate by Isaac, thrig, RalfFriedl, Filipe Brandenburger, muru yesterday
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
add a comment |
up vote
10
down vote
favorite
This question already has an answer here:
How does printf with multiple arguments separated by space work
1 answer
$ printf "%s" a b
ab$ printf "%s%s" a b
ab
I have some problem understand the format specifier for printf. If I am correct it is mostly the same as those for strings in the C programming language.
Why does the format specifier %s concatenate the two following strings together?
Why does %s not mean that there is only one string to substitute it, and ignore the remaining string?
Why are the results for two strings under %s and under %s%s the same?
bash printf
edited 2 days ago
Rui F Ribeiro
38.2k1475125
asked 2 days ago
Ben
2788
New contributor
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
marked as duplicate by Isaac, thrig, RalfFriedl, Filipe Brandenburger, muru yesterday
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
What do you get if you doprintf "%s 123" "hello" "world", yes it surprised me as well, but it is in the manual.
– ctrl-alt-delor
2 days ago
add a comment |
up vote
10
down vote
favorite
up vote
10
down vote
favorite
This question already has an answer here:
How does printf with multiple arguments separated by space work
1 answer
$ printf "%s" a b
ab$ printf "%s%s" a b
ab
I have some problem understand the format specifier for printf. If I am correct it is mostly the same as those for strings in the C programming language.
Why does the format specifier %s concatenate the two following strings together?
Why does %s not mean that there is only one string to substitute it, and ignore the remaining string?
Why are the results for two strings under %s and under %s%s the same?
bash printf
edited 2 days ago
Rui F Ribeiro
38.2k1475125
asked 2 days ago
Ben
2788
New contributor
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
This question already has an answer here:
How does printf with multiple arguments separated by space work
1 answer
$ printf "%s" a b
ab$ printf "%s%s" a b
ab
I have some problem understand the format specifier for printf. If I am correct it is mostly the same as those for strings in the C programming language.
Why does the format specifier %s concatenate the two following strings together?
Why does %s not mean that there is only one string to substitute it, and ignore the remaining string?
Why are the results for two strings under %s and under %s%s the same?
This question already has an answer here:
How does printf with multiple arguments separated by space work
1 answer
bash printf
bash printf
edited 2 days ago
Rui F Ribeiro
38.2k1475125
asked 2 days ago
Ben
2788
New contributor
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 2 days ago
Rui F Ribeiro
38.2k1475125
asked 2 days ago
Ben
2788
New contributor
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 2 days ago
Rui F Ribeiro
38.2k1475125
edited 2 days ago
Rui F Ribeiro
38.2k1475125
edited 2 days ago
Rui F Ribeiro
38.2k1475125
38.2k1475125
asked 2 days ago
Ben
2788
New contributor
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 2 days ago
Ben
2788
asked 2 days ago
Ben
2788
2788
New contributor
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Ben is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
marked as duplicate by Isaac, thrig, RalfFriedl, Filipe Brandenburger, muru yesterday
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
marked as duplicate by Isaac, thrig, RalfFriedl, Filipe Brandenburger, muru yesterday
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
What do you get if you doprintf "%s 123" "hello" "world", yes it surprised me as well, but it is in the manual.
– ctrl-alt-delor
2 days ago
add a comment |
What do you get if you doprintf "%s 123" "hello" "world", yes it surprised me as well, but it is in the manual.
– ctrl-alt-delor
2 days ago
What do you get if you do
printf "%s 123" "hello" "world", yes it surprised me as well, but it is in the manual.– ctrl-alt-delor
2 days ago
What do you get if you do
printf "%s 123" "hello" "world", yes it surprised me as well, but it is in the manual.– ctrl-alt-delor
2 days ago
add a comment |
2 Answers
2
active
oldest
votes
up vote
14
down vote
accepted
That’s how printf is specified to behave:
The format operand shall be reused as often as necessary to satisfy the argument operands. Any extra b, c, or s conversion specifiers shall be evaluated as if a null string argument were supplied; other extra conversion specifications shall be evaluated as if a zero argument were supplied. If the format operand contains no conversion specifications and argument operands are present, the results are unspecified.
In your case, the %s format is repeated as many times as necessary to handle all the arguments.
printf "%s" a b
and
printf "%s%s" a b
produce the same result because in the first case, %s is repeated twice, which is equivalent to %s%s.
answered 2 days ago
Stephen Kitt
158k23345421
Does format specifier in C also work in the same or similiar way?
– Ben
2 days ago
6
No, it doesn’t — it ignores extra arguments. Modern C compilers will warn about mismatches between the format string and the arguments.
– Stephen Kitt
2 days ago
5
@Ben in C, theprintffunction is a variadic function: all the parameters but the first are accepted via.... This means that unless told via the first argument how many are present (and which types), the function can't ever know what the caller has passed to it. In the shell the command knows exactly how many command-line arguments it has.
– Ruslan
2 days ago
add a comment |
up vote
7
down vote
If you supply more parameters to printf than the format string expects then the format string is repeated.
For example
$ printf "%s -- %s" a b c d e
a -- bc -- de --
We can see that the %s -- %s format is effectively repeated.
This can be useful; eg for formatting
$ printf "%s -- %sn" a b c d e
a -- b
c -- d
e --
answered 2 days ago
Stephen Harris
23k24176
add a comment |
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
14
down vote
accepted
That’s how printf is specified to behave:
The format operand shall be reused as often as necessary to satisfy the argument operands. Any extra b, c, or s conversion specifiers shall be evaluated as if a null string argument were supplied; other extra conversion specifications shall be evaluated as if a zero argument were supplied. If the format operand contains no conversion specifications and argument operands are present, the results are unspecified.
In your case, the %s format is repeated as many times as necessary to handle all the arguments.
printf "%s" a b
and
printf "%s%s" a b
produce the same result because in the first case, %s is repeated twice, which is equivalent to %s%s.
answered 2 days ago
Stephen Kitt
158k23345421
Does format specifier in C also work in the same or similiar way?
– Ben
2 days ago
6
No, it doesn’t — it ignores extra arguments. Modern C compilers will warn about mismatches between the format string and the arguments.
– Stephen Kitt
2 days ago
5
@Ben in C, theprintffunction is a variadic function: all the parameters but the first are accepted via.... This means that unless told via the first argument how many are present (and which types), the function can't ever know what the caller has passed to it. In the shell the command knows exactly how many command-line arguments it has.
– Ruslan
2 days ago
add a comment |
up vote
14
down vote
accepted
That’s how printf is specified to behave:
The format operand shall be reused as often as necessary to satisfy the argument operands. Any extra b, c, or s conversion specifiers shall be evaluated as if a null string argument were supplied; other extra conversion specifications shall be evaluated as if a zero argument were supplied. If the format operand contains no conversion specifications and argument operands are present, the results are unspecified.
In your case, the %s format is repeated as many times as necessary to handle all the arguments.
printf "%s" a b
and
printf "%s%s" a b
produce the same result because in the first case, %s is repeated twice, which is equivalent to %s%s.
answered 2 days ago
Stephen Kitt
158k23345421
Does format specifier in C also work in the same or similiar way?
– Ben
2 days ago
6
No, it doesn’t — it ignores extra arguments. Modern C compilers will warn about mismatches between the format string and the arguments.
– Stephen Kitt
2 days ago
5
@Ben in C, theprintffunction is a variadic function: all the parameters but the first are accepted via.... This means that unless told via the first argument how many are present (and which types), the function can't ever know what the caller has passed to it. In the shell the command knows exactly how many command-line arguments it has.
– Ruslan
2 days ago
add a comment |
up vote
14
down vote
accepted
up vote
14
down vote
accepted
That’s how printf is specified to behave:
The format operand shall be reused as often as necessary to satisfy the argument operands. Any extra b, c, or s conversion specifiers shall be evaluated as if a null string argument were supplied; other extra conversion specifications shall be evaluated as if a zero argument were supplied. If the format operand contains no conversion specifications and argument operands are present, the results are unspecified.
In your case, the %s format is repeated as many times as necessary to handle all the arguments.
printf "%s" a b
and
printf "%s%s" a b
produce the same result because in the first case, %s is repeated twice, which is equivalent to %s%s.
answered 2 days ago
Stephen Kitt
158k23345421
That’s how printf is specified to behave:
The format operand shall be reused as often as necessary to satisfy the argument operands. Any extra b, c, or s conversion specifiers shall be evaluated as if a null string argument were supplied; other extra conversion specifications shall be evaluated as if a zero argument were supplied. If the format operand contains no conversion specifications and argument operands are present, the results are unspecified.
In your case, the %s format is repeated as many times as necessary to handle all the arguments.
printf "%s" a b
and
printf "%s%s" a b
produce the same result because in the first case, %s is repeated twice, which is equivalent to %s%s.
answered 2 days ago
Stephen Kitt
158k23345421
answered 2 days ago
Stephen Kitt
158k23345421
answered 2 days ago
Stephen Kitt
158k23345421
answered 2 days ago
Stephen Kitt
158k23345421
158k23345421
Does format specifier in C also work in the same or similiar way?
– Ben
2 days ago
6
No, it doesn’t — it ignores extra arguments. Modern C compilers will warn about mismatches between the format string and the arguments.
– Stephen Kitt
2 days ago
5
@Ben in C, theprintffunction is a variadic function: all the parameters but the first are accepted via.... This means that unless told via the first argument how many are present (and which types), the function can't ever know what the caller has passed to it. In the shell the command knows exactly how many command-line arguments it has.
– Ruslan
2 days ago
add a comment |
Does format specifier in C also work in the same or similiar way?
– Ben
2 days ago
6
No, it doesn’t — it ignores extra arguments. Modern C compilers will warn about mismatches between the format string and the arguments.
– Stephen Kitt
2 days ago
5
@Ben in C, theprintffunction is a variadic function: all the parameters but the first are accepted via.... This means that unless told via the first argument how many are present (and which types), the function can't ever know what the caller has passed to it. In the shell the command knows exactly how many command-line arguments it has.
– Ruslan
2 days ago
Does format specifier in C also work in the same or similiar way?
– Ben
2 days ago
Does format specifier in C also work in the same or similiar way?
– Ben
2 days ago
6
6
No, it doesn’t — it ignores extra arguments. Modern C compilers will warn about mismatches between the format string and the arguments.
– Stephen Kitt
2 days ago
No, it doesn’t — it ignores extra arguments. Modern C compilers will warn about mismatches between the format string and the arguments.
– Stephen Kitt
2 days ago
5
5
@Ben in C, the
printf function is a variadic function: all the parameters but the first are accepted via .... This means that unless told via the first argument how many are present (and which types), the function can't ever know what the caller has passed to it. In the shell the command knows exactly how many command-line arguments it has.– Ruslan
2 days ago
@Ben in C, the
printf function is a variadic function: all the parameters but the first are accepted via .... This means that unless told via the first argument how many are present (and which types), the function can't ever know what the caller has passed to it. In the shell the command knows exactly how many command-line arguments it has.– Ruslan
2 days ago
add a comment |
up vote
7
down vote
If you supply more parameters to printf than the format string expects then the format string is repeated.
For example
$ printf "%s -- %s" a b c d e
a -- bc -- de --
We can see that the %s -- %s format is effectively repeated.
This can be useful; eg for formatting
$ printf "%s -- %sn" a b c d e
a -- b
c -- d
e --
answered 2 days ago
Stephen Harris
23k24176
add a comment |
up vote
7
down vote
If you supply more parameters to printf than the format string expects then the format string is repeated.
For example
$ printf "%s -- %s" a b c d e
a -- bc -- de --
We can see that the %s -- %s format is effectively repeated.
This can be useful; eg for formatting
$ printf "%s -- %sn" a b c d e
a -- b
c -- d
e --
answered 2 days ago
Stephen Harris
23k24176
add a comment |
up vote
7
down vote
up vote
7
down vote
If you supply more parameters to printf than the format string expects then the format string is repeated.
For example
$ printf "%s -- %s" a b c d e
a -- bc -- de --
We can see that the %s -- %s format is effectively repeated.
This can be useful; eg for formatting
$ printf "%s -- %sn" a b c d e
a -- b
c -- d
e --
answered 2 days ago
Stephen Harris
23k24176
If you supply more parameters to printf than the format string expects then the format string is repeated.
For example
$ printf "%s -- %s" a b c d e
a -- bc -- de --
We can see that the %s -- %s format is effectively repeated.
This can be useful; eg for formatting
$ printf "%s -- %sn" a b c d e
a -- b
c -- d
e --
answered 2 days ago
Stephen Harris
23k24176
answered 2 days ago
Stephen Harris
23k24176
answered 2 days ago
Stephen Harris
23k24176
answered 2 days ago
Stephen Harris
23k24176
23k24176
add a comment |
add a comment |
What do you get if you do
printf "%s 123" "hello" "world", yes it surprised me as well, but it is in the manual.– ctrl-alt-delor
2 days ago