Related
This
STR="Hello\nWorld"
echo $STR
produces as output
Hello\nWorld
instead of
Hello
World
What should I do to have a newline in a string?
Note: This question is not about echo.
I'm aware of echo -e, but I'm looking for a solution that allows passing a string (which includes a newline) as an argument to other commands that do not have a similar option to interpret \n's as newlines.
If you're using Bash, you can use backslash-escapes inside of a specially-quoted $'string'. For example, adding \n:
STR=$'Hello\nWorld'
echo "$STR" # quotes are required here!
Prints:
Hello
World
If you're using pretty much any other shell, just insert the newline as-is in the string:
STR='Hello
World'
Bash recognizes a number of other backslash escape sequences in the $'' string. Here is an excerpt from the Bash manual page:
Words of the form $'string' are treated specially. The word expands to
string, with backslash-escaped characters replaced as specified by the
ANSI C standard. Backslash escape sequences, if present, are decoded
as follows:
\a alert (bell)
\b backspace
\e
\E an escape character
\f form feed
\n new line
\r carriage return
\t horizontal tab
\v vertical tab
\\ backslash
\' single quote
\" double quote
\nnn the eight-bit character whose value is the octal value
nnn (one to three digits)
\xHH the eight-bit character whose value is the hexadecimal
value HH (one or two hex digits)
\cx a control-x character
The expanded result is single-quoted, as if the dollar sign had not
been present.
A double-quoted string preceded by a dollar sign ($"string") will cause
the string to be translated according to the current locale. If the
current locale is C or POSIX, the dollar sign is ignored. If the
string is translated and replaced, the replacement is double-quoted.
Echo is so nineties and so fraught with perils that its use should result in core dumps no less than 4GB. Seriously, echo's problems were the reason why the Unix Standardization process finally invented the printf utility, doing away with all the problems.
So to get a newline in a string, there are two ways:
# 1) Literal newline in an assignment.
FOO="hello
world"
# 2) Command substitution.
BAR=$(printf "hello\nworld\n") # Alternative; note: final newline is deleted
printf '<%s>\n' "$FOO"
printf '<%s>\n' "$BAR"
There! No SYSV vs BSD echo madness, everything gets neatly printed and fully portable support for C escape sequences. Everybody please use printf now for all your output needs and never look back.
What I did based on the other answers was
NEWLINE=$'\n'
my_var="__between eggs and bacon__"
echo "spam${NEWLINE}eggs${my_var}bacon${NEWLINE}knight"
# which outputs:
spam
eggs__between eggs and bacon__bacon
knight
I find the -e flag elegant and straight forward
bash$ STR="Hello\nWorld"
bash$ echo -e $STR
Hello
World
If the string is the output of another command, I just use quotes
indexes_diff=$(git diff index.yaml)
echo "$indexes_diff"
The problem isn't with the shell. The problem is actually with the echo command itself, and the lack of double quotes around the variable interpolation. You can try using echo -e but that isn't supported on all platforms, and one of the reasons printf is now recommended for portability.
You can also try and insert the newline directly into your shell script (if a script is what you're writing) so it looks like...
#!/bin/sh
echo "Hello
World"
#EOF
or equivalently
#!/bin/sh
string="Hello
World"
echo "$string" # note double quotes!
The only simple alternative is to actually type a new line in the variable:
$ STR='new
line'
$ printf '%s' "$STR"
new
line
Yes, that means writing Enter where needed in the code.
There are several equivalents to a new line character.
\n ### A common way to represent a new line character.
\012 ### Octal value of a new line character.
\x0A ### Hexadecimal value of a new line character.
But all those require "an interpretation" by some tool (POSIX printf):
echo -e "new\nline" ### on POSIX echo, `-e` is not required.
printf 'new\nline' ### Understood by POSIX printf.
printf 'new\012line' ### Valid in POSIX printf.
printf 'new\x0Aline'
printf '%b' 'new\0012line' ### Valid in POSIX printf.
And therefore, the tool is required to build a string with a new-line:
$ STR="$(printf 'new\nline')"
$ printf '%s' "$STR"
new
line
In some shells, the sequence $' is a special shell expansion.
Known to work in ksh93, bash and zsh:
$ STR=$'new\nline'
Of course, more complex solutions are also possible:
$ echo '6e65770a6c696e650a' | xxd -p -r
new
line
Or
$ echo "new line" | sed 's/ \+/\n/g'
new
line
A $ right before single quotation marks '...\n...' as follows, however double quotation marks doesn't work.
$ echo $'Hello\nWorld'
Hello
World
$ echo $"Hello\nWorld"
Hello\nWorld
Disclaimer: I first wrote this and then stumbled upon this question. I thought this solution wasn't yet posted, and saw that tlwhitec did post a similar answer. Still I'm posting this because I hope it's a useful and thorough explanation.
Short answer:
This seems quite a portable solution, as it works on quite some shells (see comment).
This way you can get a real newline into a variable.
The benefit of this solution is that you don't have to use newlines in your source code, so you can indent
your code any way you want, and the solution still works. This makes it robust. It's also portable.
# Robust way to put a real newline in a variable (bash, dash, ksh, zsh; indentation-resistant).
nl="$(printf '\nq')"
nl=${nl%q}
Longer answer:
Explanation of the above solution:
The newline would normally be lost due to command substitution, but to prevent that, we add a 'q' and remove it afterwards. (The reason for the double quotes is explained further below.)
We can prove that the variable contains an actual newline character (0x0A):
printf '%s' "$nl" | hexdump -C
00000000 0a |.|
00000001
(Note that the '%s' was needed, otherwise printf will translate a literal '\n' string into an actual 0x0A character, meaning we would prove nothing.)
Of course, instead of the solution proposed in this answer, one could use this as well (but...):
nl='
'
... but that's less robust and can be easily damaged by accidentally indenting the code, or by forgetting to outdent it afterwards, which makes it inconvenient to use in (indented) functions, whereas the earlier solution is robust.
Now, as for the double quotes:
The reason for the double quotes " surrounding the command substitution as in nl="$(printf '\nq')" is that you can then even prefix the variable assignment with the local keyword or builtin (such as in functions), and it will still work on all shells, whereas otherwise the dash shell would have trouble, in the sense that dash would otherwise lose the 'q' and you'd end up with an empty 'nl' variable (again, due to command substitution).
That issue is better illustrated with another example:
dash_trouble_example() {
e=$(echo hello world) # Not using 'local'.
echo "$e" # Fine. Outputs 'hello world' in all shells.
local e=$(echo hello world) # But now, when using 'local' without double quotes ...:
echo "$e" # ... oops, outputs just 'hello' in dash,
# ... but 'hello world' in bash and zsh.
local f="$(echo hello world)" # Finally, using 'local' and surrounding with double quotes.
echo "$f" # Solved. Outputs 'hello world' in dash, zsh, and bash.
# So back to our newline example, if we want to use 'local', we need
# double quotes to surround the command substitution:
# (If we didn't use double quotes here, then in dash the 'nl' variable
# would be empty.)
local nl="$(printf '\nq')"
nl=${nl%q}
}
Practical example of the above solution:
# Parsing lines in a for loop by setting IFS to a real newline character:
nl="$(printf '\nq')"
nl=${nl%q}
IFS=$nl
for i in $(printf '%b' 'this is line 1\nthis is line 2'); do
echo "i=$i"
done
# Desired output:
# i=this is line 1
# i=this is line 2
# Exercise:
# Try running this example without the IFS=$nl assignment, and predict the outcome.
I'm no bash expert, but this one worked for me:
STR1="Hello"
STR2="World"
NEWSTR=$(cat << EOF
$STR1
$STR2
EOF
)
echo "$NEWSTR"
I found this easier to formatting the texts.
Those picky ones that need just the newline and despise the multiline code that breaks indentation, could do:
IFS="$(printf '\nx')"
IFS="${IFS%x}"
Bash (and likely other shells) gobble all the trailing newlines after command substitution, so you need to end the printf string with a non-newline character and delete it afterwards. This can also easily become a oneliner.
IFS="$(printf '\nx')" IFS="${IFS%x}"
I know this is two actions instead of one, but my indentation and portability OCD is at peace now :) I originally developed this to be able to split newline-only separated output and I ended up using a modification that uses \r as the terminating character. That makes the newline splitting work even for the dos output ending with \r\n.
IFS="$(printf '\n\r')"
On my system (Ubuntu 17.10) your example just works as desired, both when typed from the command line (into sh) and when executed as a sh script:
[bash]§ sh
$ STR="Hello\nWorld"
$ echo $STR
Hello
World
$ exit
[bash]§ echo "STR=\"Hello\nWorld\"
> echo \$STR" > test-str.sh
[bash]§ cat test-str.sh
STR="Hello\nWorld"
echo $STR
[bash]§ sh test-str.sh
Hello
World
I guess this answers your question: it just works. (I have not tried to figure out details such as at what moment exactly the substitution of the newline character for \n happens in sh).
However, i noticed that this same script would behave differently when executed with bash and would print out Hello\nWorld instead:
[bash]§ bash test-str.sh
Hello\nWorld
I've managed to get the desired output with bash as follows:
[bash]§ STR="Hello
> World"
[bash]§ echo "$STR"
Note the double quotes around $STR. This behaves identically if saved and run as a bash script.
The following also gives the desired output:
[bash]§ echo "Hello
> World"
I wasn't really happy with any of the options here. This is what worked for me.
str=$(printf "%s" "first line")
str=$(printf "$str\n%s" "another line")
str=$(printf "$str\n%s" "and another line")
This isn't ideal, but I had written a lot of code and defined strings in a way similar to the method used in the question. The accepted solution required me to refactor a lot of the code so instead, I replaced every \n with "$'\n'" and this worked for me.
I need my script to send an email from terminal. Based on what I've seen here and many other places online, I formatted it like this:
/var/mail -s "$SUBJECT" "$EMAIL" << EOF
Here's a line of my message!
And here's another line!
Last line of the message here!
EOF
However, when I run this I get this warning:
myfile.sh: line x: warning: here-document at line y delimited by end-of-file (wanted 'EOF')
myfile.sh: line x+1: syntax error: unexpected end of file
...where line x is the last written line of code in the program, and line y is the line with /var/mail in it. I've tried replacing EOF with other things (ENDOFMESSAGE, FINISH, etc.) but to no avail. Nearly everything I've found online has it done this way, and I'm really new at bash so I'm having a hard time figuring it out on my own. Could anyone offer any help?
The EOF token must be at the beginning of the line, you can't indent it along with the block of code it goes with.
If you write <<-EOF you may indent it, but it must be indented with Tab characters, not spaces. So it still might not end up even with the block of code.
Also make sure you have no whitespace after the EOF token on the line.
The line that starts or ends the here-doc probably has some non-printable or whitespace characters (for example, carriage return) which means that the second "EOF" does not match the first, and doesn't end the here-doc like it should. This is a very common error, and difficult to detect with just a text editor. You can make non-printable characters visible for example with cat:
cat -A myfile.sh
Once you see the output from cat -A the solution will be obvious: remove the offending characters.
Please try to remove the preceeding spaces before EOF:-
/var/mail -s "$SUBJECT" "$EMAIL" <<-EOF
Using <tab> instead of <spaces> for ident AND using <<-EOF works fine.
The "-" removes the <tabs>, not <spaces>, but at least this works.
Note one can also get this error if you do this;
while read line; do
echo $line
done << somefile
Because << somefile should read < somefile in this case.
May be old but I had a space after the ending EOF
<< EOF
blah
blah
EOF <-- this was the issue. Had it for years, finally looked it up here
For anyone stumbling here who googled "bash warning: here-document delimited by end-of-file", it may be that you are getting the
warning: here-document at line 74 delimited by end-of-file
...type warning because you accidentally used a here document symbol (<<) when you meant to use a here string symbol (<<<). That was my case.
Here is a flexible way to do deal with multiple indented lines without using heredoc.
echo 'Hello!'
sed -e 's:^\s*::' < <(echo '
Some indented text here.
Some indented text here.
')
if [[ true ]]; then
sed -e 's:^\s\{4,4\}::' < <(echo '
Some indented text here.
Some extra indented text here.
Some indented text here.
')
fi
Some notes on this solution:
if the content is expected to have simple quotes, either escape them using \ or replace the string delimiters with double quotes. In the latter case, be careful that construction like $(command) will be interpreted. If the string contains both simple and double quotes, you'll have to escape at least of kind.
the given example print a trailing empty line, there are numerous way to get rid of it, not included here to keep the proposal to a minimum clutter
the flexibility comes from the ease with which you can control how much leading space should stay or go, provided that you know some sed REGEXP of course.
When I want to have docstrings for my bash functions, I use a solution similar to the suggestion of user12205 in a duplicate of this question.
See how I define USAGE for a solution that:
auto-formats well for me in my IDE of choice (sublime)
is multi-line
can use spaces or tabs as indentation
preserves indentations within the comment.
function foo {
# Docstring
read -r -d '' USAGE <<' END'
# This method prints foo to the terminal.
#
# Enter `foo -h` to see the docstring.
# It has indentations and multiple lines.
#
# Change the delimiter if you need hashtag for some reason.
# This can include $$ and = and eval, but won't be evaluated
END
if [ "$1" = "-h" ]
then
echo "$USAGE" | cut -d "#" -f 2 | cut -c 2-
return
fi
echo "foo"
}
So foo -h yields:
This method prints foo to the terminal.
Enter `foo -h` to see the docstring.
It has indentations and multiple lines.
Change the delimiter if you need hashtag for some reason.
This can include $$ and = and eval, but won't be evaluated
Explanation
cut -d "#" -f 2: Retrieve the second portion of the # delimited lines. (Think a csv with "#" as the delimiter, empty first column).
cut -c 2-: Retrieve the 2nd to end character of the resultant string
Also note that if [ "$1" = "-h" ] evaluates as False if there is no first argument, w/o error, since it becomes an empty string.
make sure where you put the ending EOF you put it at the beginning of a new line
Along with the other answers mentioned by Barmar and Joni, I've noticed that I sometimes have to leave a blank line before and after my EOF when using <<-EOF.
This
STR="Hello\nWorld"
echo $STR
produces as output
Hello\nWorld
instead of
Hello
World
What should I do to have a newline in a string?
Note: This question is not about echo.
I'm aware of echo -e, but I'm looking for a solution that allows passing a string (which includes a newline) as an argument to other commands that do not have a similar option to interpret \n's as newlines.
If you're using Bash, you can use backslash-escapes inside of a specially-quoted $'string'. For example, adding \n:
STR=$'Hello\nWorld'
echo "$STR" # quotes are required here!
Prints:
Hello
World
If you're using pretty much any other shell, just insert the newline as-is in the string:
STR='Hello
World'
Bash recognizes a number of other backslash escape sequences in the $'' string. Here is an excerpt from the Bash manual page:
Words of the form $'string' are treated specially. The word expands to
string, with backslash-escaped characters replaced as specified by the
ANSI C standard. Backslash escape sequences, if present, are decoded
as follows:
\a alert (bell)
\b backspace
\e
\E an escape character
\f form feed
\n new line
\r carriage return
\t horizontal tab
\v vertical tab
\\ backslash
\' single quote
\" double quote
\nnn the eight-bit character whose value is the octal value
nnn (one to three digits)
\xHH the eight-bit character whose value is the hexadecimal
value HH (one or two hex digits)
\cx a control-x character
The expanded result is single-quoted, as if the dollar sign had not
been present.
A double-quoted string preceded by a dollar sign ($"string") will cause
the string to be translated according to the current locale. If the
current locale is C or POSIX, the dollar sign is ignored. If the
string is translated and replaced, the replacement is double-quoted.
Echo is so nineties and so fraught with perils that its use should result in core dumps no less than 4GB. Seriously, echo's problems were the reason why the Unix Standardization process finally invented the printf utility, doing away with all the problems.
So to get a newline in a string, there are two ways:
# 1) Literal newline in an assignment.
FOO="hello
world"
# 2) Command substitution.
BAR=$(printf "hello\nworld\n") # Alternative; note: final newline is deleted
printf '<%s>\n' "$FOO"
printf '<%s>\n' "$BAR"
There! No SYSV vs BSD echo madness, everything gets neatly printed and fully portable support for C escape sequences. Everybody please use printf now for all your output needs and never look back.
What I did based on the other answers was
NEWLINE=$'\n'
my_var="__between eggs and bacon__"
echo "spam${NEWLINE}eggs${my_var}bacon${NEWLINE}knight"
# which outputs:
spam
eggs__between eggs and bacon__bacon
knight
I find the -e flag elegant and straight forward
bash$ STR="Hello\nWorld"
bash$ echo -e $STR
Hello
World
If the string is the output of another command, I just use quotes
indexes_diff=$(git diff index.yaml)
echo "$indexes_diff"
The problem isn't with the shell. The problem is actually with the echo command itself, and the lack of double quotes around the variable interpolation. You can try using echo -e but that isn't supported on all platforms, and one of the reasons printf is now recommended for portability.
You can also try and insert the newline directly into your shell script (if a script is what you're writing) so it looks like...
#!/bin/sh
echo "Hello
World"
#EOF
or equivalently
#!/bin/sh
string="Hello
World"
echo "$string" # note double quotes!
The only simple alternative is to actually type a new line in the variable:
$ STR='new
line'
$ printf '%s' "$STR"
new
line
Yes, that means writing Enter where needed in the code.
There are several equivalents to a new line character.
\n ### A common way to represent a new line character.
\012 ### Octal value of a new line character.
\x0A ### Hexadecimal value of a new line character.
But all those require "an interpretation" by some tool (POSIX printf):
echo -e "new\nline" ### on POSIX echo, `-e` is not required.
printf 'new\nline' ### Understood by POSIX printf.
printf 'new\012line' ### Valid in POSIX printf.
printf 'new\x0Aline'
printf '%b' 'new\0012line' ### Valid in POSIX printf.
And therefore, the tool is required to build a string with a new-line:
$ STR="$(printf 'new\nline')"
$ printf '%s' "$STR"
new
line
In some shells, the sequence $' is a special shell expansion.
Known to work in ksh93, bash and zsh:
$ STR=$'new\nline'
Of course, more complex solutions are also possible:
$ echo '6e65770a6c696e650a' | xxd -p -r
new
line
Or
$ echo "new line" | sed 's/ \+/\n/g'
new
line
A $ right before single quotation marks '...\n...' as follows, however double quotation marks doesn't work.
$ echo $'Hello\nWorld'
Hello
World
$ echo $"Hello\nWorld"
Hello\nWorld
Disclaimer: I first wrote this and then stumbled upon this question. I thought this solution wasn't yet posted, and saw that tlwhitec did post a similar answer. Still I'm posting this because I hope it's a useful and thorough explanation.
Short answer:
This seems quite a portable solution, as it works on quite some shells (see comment).
This way you can get a real newline into a variable.
The benefit of this solution is that you don't have to use newlines in your source code, so you can indent
your code any way you want, and the solution still works. This makes it robust. It's also portable.
# Robust way to put a real newline in a variable (bash, dash, ksh, zsh; indentation-resistant).
nl="$(printf '\nq')"
nl=${nl%q}
Longer answer:
Explanation of the above solution:
The newline would normally be lost due to command substitution, but to prevent that, we add a 'q' and remove it afterwards. (The reason for the double quotes is explained further below.)
We can prove that the variable contains an actual newline character (0x0A):
printf '%s' "$nl" | hexdump -C
00000000 0a |.|
00000001
(Note that the '%s' was needed, otherwise printf will translate a literal '\n' string into an actual 0x0A character, meaning we would prove nothing.)
Of course, instead of the solution proposed in this answer, one could use this as well (but...):
nl='
'
... but that's less robust and can be easily damaged by accidentally indenting the code, or by forgetting to outdent it afterwards, which makes it inconvenient to use in (indented) functions, whereas the earlier solution is robust.
Now, as for the double quotes:
The reason for the double quotes " surrounding the command substitution as in nl="$(printf '\nq')" is that you can then even prefix the variable assignment with the local keyword or builtin (such as in functions), and it will still work on all shells, whereas otherwise the dash shell would have trouble, in the sense that dash would otherwise lose the 'q' and you'd end up with an empty 'nl' variable (again, due to command substitution).
That issue is better illustrated with another example:
dash_trouble_example() {
e=$(echo hello world) # Not using 'local'.
echo "$e" # Fine. Outputs 'hello world' in all shells.
local e=$(echo hello world) # But now, when using 'local' without double quotes ...:
echo "$e" # ... oops, outputs just 'hello' in dash,
# ... but 'hello world' in bash and zsh.
local f="$(echo hello world)" # Finally, using 'local' and surrounding with double quotes.
echo "$f" # Solved. Outputs 'hello world' in dash, zsh, and bash.
# So back to our newline example, if we want to use 'local', we need
# double quotes to surround the command substitution:
# (If we didn't use double quotes here, then in dash the 'nl' variable
# would be empty.)
local nl="$(printf '\nq')"
nl=${nl%q}
}
Practical example of the above solution:
# Parsing lines in a for loop by setting IFS to a real newline character:
nl="$(printf '\nq')"
nl=${nl%q}
IFS=$nl
for i in $(printf '%b' 'this is line 1\nthis is line 2'); do
echo "i=$i"
done
# Desired output:
# i=this is line 1
# i=this is line 2
# Exercise:
# Try running this example without the IFS=$nl assignment, and predict the outcome.
I'm no bash expert, but this one worked for me:
STR1="Hello"
STR2="World"
NEWSTR=$(cat << EOF
$STR1
$STR2
EOF
)
echo "$NEWSTR"
I found this easier to formatting the texts.
Those picky ones that need just the newline and despise the multiline code that breaks indentation, could do:
IFS="$(printf '\nx')"
IFS="${IFS%x}"
Bash (and likely other shells) gobble all the trailing newlines after command substitution, so you need to end the printf string with a non-newline character and delete it afterwards. This can also easily become a oneliner.
IFS="$(printf '\nx')" IFS="${IFS%x}"
I know this is two actions instead of one, but my indentation and portability OCD is at peace now :) I originally developed this to be able to split newline-only separated output and I ended up using a modification that uses \r as the terminating character. That makes the newline splitting work even for the dos output ending with \r\n.
IFS="$(printf '\n\r')"
On my system (Ubuntu 17.10) your example just works as desired, both when typed from the command line (into sh) and when executed as a sh script:
[bash]§ sh
$ STR="Hello\nWorld"
$ echo $STR
Hello
World
$ exit
[bash]§ echo "STR=\"Hello\nWorld\"
> echo \$STR" > test-str.sh
[bash]§ cat test-str.sh
STR="Hello\nWorld"
echo $STR
[bash]§ sh test-str.sh
Hello
World
I guess this answers your question: it just works. (I have not tried to figure out details such as at what moment exactly the substitution of the newline character for \n happens in sh).
However, i noticed that this same script would behave differently when executed with bash and would print out Hello\nWorld instead:
[bash]§ bash test-str.sh
Hello\nWorld
I've managed to get the desired output with bash as follows:
[bash]§ STR="Hello
> World"
[bash]§ echo "$STR"
Note the double quotes around $STR. This behaves identically if saved and run as a bash script.
The following also gives the desired output:
[bash]§ echo "Hello
> World"
I wasn't really happy with any of the options here. This is what worked for me.
str=$(printf "%s" "first line")
str=$(printf "$str\n%s" "another line")
str=$(printf "$str\n%s" "and another line")
This isn't ideal, but I had written a lot of code and defined strings in a way similar to the method used in the question. The accepted solution required me to refactor a lot of the code so instead, I replaced every \n with "$'\n'" and this worked for me.
This
STR="Hello\nWorld"
echo $STR
produces as output
Hello\nWorld
instead of
Hello
World
What should I do to have a newline in a string?
Note: This question is not about echo.
I'm aware of echo -e, but I'm looking for a solution that allows passing a string (which includes a newline) as an argument to other commands that do not have a similar option to interpret \n's as newlines.
If you're using Bash, you can use backslash-escapes inside of a specially-quoted $'string'. For example, adding \n:
STR=$'Hello\nWorld'
echo "$STR" # quotes are required here!
Prints:
Hello
World
If you're using pretty much any other shell, just insert the newline as-is in the string:
STR='Hello
World'
Bash recognizes a number of other backslash escape sequences in the $'' string. Here is an excerpt from the Bash manual page:
Words of the form $'string' are treated specially. The word expands to
string, with backslash-escaped characters replaced as specified by the
ANSI C standard. Backslash escape sequences, if present, are decoded
as follows:
\a alert (bell)
\b backspace
\e
\E an escape character
\f form feed
\n new line
\r carriage return
\t horizontal tab
\v vertical tab
\\ backslash
\' single quote
\" double quote
\nnn the eight-bit character whose value is the octal value
nnn (one to three digits)
\xHH the eight-bit character whose value is the hexadecimal
value HH (one or two hex digits)
\cx a control-x character
The expanded result is single-quoted, as if the dollar sign had not
been present.
A double-quoted string preceded by a dollar sign ($"string") will cause
the string to be translated according to the current locale. If the
current locale is C or POSIX, the dollar sign is ignored. If the
string is translated and replaced, the replacement is double-quoted.
Echo is so nineties and so fraught with perils that its use should result in core dumps no less than 4GB. Seriously, echo's problems were the reason why the Unix Standardization process finally invented the printf utility, doing away with all the problems.
So to get a newline in a string, there are two ways:
# 1) Literal newline in an assignment.
FOO="hello
world"
# 2) Command substitution.
BAR=$(printf "hello\nworld\n") # Alternative; note: final newline is deleted
printf '<%s>\n' "$FOO"
printf '<%s>\n' "$BAR"
There! No SYSV vs BSD echo madness, everything gets neatly printed and fully portable support for C escape sequences. Everybody please use printf now for all your output needs and never look back.
What I did based on the other answers was
NEWLINE=$'\n'
my_var="__between eggs and bacon__"
echo "spam${NEWLINE}eggs${my_var}bacon${NEWLINE}knight"
# which outputs:
spam
eggs__between eggs and bacon__bacon
knight
I find the -e flag elegant and straight forward
bash$ STR="Hello\nWorld"
bash$ echo -e $STR
Hello
World
If the string is the output of another command, I just use quotes
indexes_diff=$(git diff index.yaml)
echo "$indexes_diff"
The problem isn't with the shell. The problem is actually with the echo command itself, and the lack of double quotes around the variable interpolation. You can try using echo -e but that isn't supported on all platforms, and one of the reasons printf is now recommended for portability.
You can also try and insert the newline directly into your shell script (if a script is what you're writing) so it looks like...
#!/bin/sh
echo "Hello
World"
#EOF
or equivalently
#!/bin/sh
string="Hello
World"
echo "$string" # note double quotes!
The only simple alternative is to actually type a new line in the variable:
$ STR='new
line'
$ printf '%s' "$STR"
new
line
Yes, that means writing Enter where needed in the code.
There are several equivalents to a new line character.
\n ### A common way to represent a new line character.
\012 ### Octal value of a new line character.
\x0A ### Hexadecimal value of a new line character.
But all those require "an interpretation" by some tool (POSIX printf):
echo -e "new\nline" ### on POSIX echo, `-e` is not required.
printf 'new\nline' ### Understood by POSIX printf.
printf 'new\012line' ### Valid in POSIX printf.
printf 'new\x0Aline'
printf '%b' 'new\0012line' ### Valid in POSIX printf.
And therefore, the tool is required to build a string with a new-line:
$ STR="$(printf 'new\nline')"
$ printf '%s' "$STR"
new
line
In some shells, the sequence $' is a special shell expansion.
Known to work in ksh93, bash and zsh:
$ STR=$'new\nline'
Of course, more complex solutions are also possible:
$ echo '6e65770a6c696e650a' | xxd -p -r
new
line
Or
$ echo "new line" | sed 's/ \+/\n/g'
new
line
A $ right before single quotation marks '...\n...' as follows, however double quotation marks doesn't work.
$ echo $'Hello\nWorld'
Hello
World
$ echo $"Hello\nWorld"
Hello\nWorld
Disclaimer: I first wrote this and then stumbled upon this question. I thought this solution wasn't yet posted, and saw that tlwhitec did post a similar answer. Still I'm posting this because I hope it's a useful and thorough explanation.
Short answer:
This seems quite a portable solution, as it works on quite some shells (see comment).
This way you can get a real newline into a variable.
The benefit of this solution is that you don't have to use newlines in your source code, so you can indent
your code any way you want, and the solution still works. This makes it robust. It's also portable.
# Robust way to put a real newline in a variable (bash, dash, ksh, zsh; indentation-resistant).
nl="$(printf '\nq')"
nl=${nl%q}
Longer answer:
Explanation of the above solution:
The newline would normally be lost due to command substitution, but to prevent that, we add a 'q' and remove it afterwards. (The reason for the double quotes is explained further below.)
We can prove that the variable contains an actual newline character (0x0A):
printf '%s' "$nl" | hexdump -C
00000000 0a |.|
00000001
(Note that the '%s' was needed, otherwise printf will translate a literal '\n' string into an actual 0x0A character, meaning we would prove nothing.)
Of course, instead of the solution proposed in this answer, one could use this as well (but...):
nl='
'
... but that's less robust and can be easily damaged by accidentally indenting the code, or by forgetting to outdent it afterwards, which makes it inconvenient to use in (indented) functions, whereas the earlier solution is robust.
Now, as for the double quotes:
The reason for the double quotes " surrounding the command substitution as in nl="$(printf '\nq')" is that you can then even prefix the variable assignment with the local keyword or builtin (such as in functions), and it will still work on all shells, whereas otherwise the dash shell would have trouble, in the sense that dash would otherwise lose the 'q' and you'd end up with an empty 'nl' variable (again, due to command substitution).
That issue is better illustrated with another example:
dash_trouble_example() {
e=$(echo hello world) # Not using 'local'.
echo "$e" # Fine. Outputs 'hello world' in all shells.
local e=$(echo hello world) # But now, when using 'local' without double quotes ...:
echo "$e" # ... oops, outputs just 'hello' in dash,
# ... but 'hello world' in bash and zsh.
local f="$(echo hello world)" # Finally, using 'local' and surrounding with double quotes.
echo "$f" # Solved. Outputs 'hello world' in dash, zsh, and bash.
# So back to our newline example, if we want to use 'local', we need
# double quotes to surround the command substitution:
# (If we didn't use double quotes here, then in dash the 'nl' variable
# would be empty.)
local nl="$(printf '\nq')"
nl=${nl%q}
}
Practical example of the above solution:
# Parsing lines in a for loop by setting IFS to a real newline character:
nl="$(printf '\nq')"
nl=${nl%q}
IFS=$nl
for i in $(printf '%b' 'this is line 1\nthis is line 2'); do
echo "i=$i"
done
# Desired output:
# i=this is line 1
# i=this is line 2
# Exercise:
# Try running this example without the IFS=$nl assignment, and predict the outcome.
I'm no bash expert, but this one worked for me:
STR1="Hello"
STR2="World"
NEWSTR=$(cat << EOF
$STR1
$STR2
EOF
)
echo "$NEWSTR"
I found this easier to formatting the texts.
Those picky ones that need just the newline and despise the multiline code that breaks indentation, could do:
IFS="$(printf '\nx')"
IFS="${IFS%x}"
Bash (and likely other shells) gobble all the trailing newlines after command substitution, so you need to end the printf string with a non-newline character and delete it afterwards. This can also easily become a oneliner.
IFS="$(printf '\nx')" IFS="${IFS%x}"
I know this is two actions instead of one, but my indentation and portability OCD is at peace now :) I originally developed this to be able to split newline-only separated output and I ended up using a modification that uses \r as the terminating character. That makes the newline splitting work even for the dos output ending with \r\n.
IFS="$(printf '\n\r')"
On my system (Ubuntu 17.10) your example just works as desired, both when typed from the command line (into sh) and when executed as a sh script:
[bash]§ sh
$ STR="Hello\nWorld"
$ echo $STR
Hello
World
$ exit
[bash]§ echo "STR=\"Hello\nWorld\"
> echo \$STR" > test-str.sh
[bash]§ cat test-str.sh
STR="Hello\nWorld"
echo $STR
[bash]§ sh test-str.sh
Hello
World
I guess this answers your question: it just works. (I have not tried to figure out details such as at what moment exactly the substitution of the newline character for \n happens in sh).
However, i noticed that this same script would behave differently when executed with bash and would print out Hello\nWorld instead:
[bash]§ bash test-str.sh
Hello\nWorld
I've managed to get the desired output with bash as follows:
[bash]§ STR="Hello
> World"
[bash]§ echo "$STR"
Note the double quotes around $STR. This behaves identically if saved and run as a bash script.
The following also gives the desired output:
[bash]§ echo "Hello
> World"
I wasn't really happy with any of the options here. This is what worked for me.
str=$(printf "%s" "first line")
str=$(printf "$str\n%s" "another line")
str=$(printf "$str\n%s" "and another line")
This isn't ideal, but I had written a lot of code and defined strings in a way similar to the method used in the question. The accepted solution required me to refactor a lot of the code so instead, I replaced every \n with "$'\n'" and this worked for me.
There are many ways to expand an escaped string, but how can a shell command be made to take a string as an argument and escape it?
Here are some examples of different ways of expansion:
$ echo -e '\x27\\012\b34\n56\\\aa7\t8\r 9\0\0134\047'
'\0134
9\'7 8
$ echo $'\x27\\012\b34\n56\\\aa7\t8\r 9\0\0134\047'
'\0134
9\a7 8
$ PS1='(5)$ ' # At least tab-width - 3 long; 5 columns given typical tab-width.
(5)$ printf %b '\x27\\012\b34\n56\\\aa7\t8\r 9\0\0134\047'
'\0134
9\'(5)$
Note: there's actually a tab character between the 7 and 8 above, but the markup rendering seems to break it.
Yes, all sorts of craziness in there. ;-)
Anyway, I'm looking for the reverse of such escape expansion commands. If the command was called escape, it would satisfy these properties:
$ echo -ne "$(escape "$originalString")"
Should output the verbatim value of originalString as would ‘echo -n "$originalString"’. I.e. it should be an identity.
Likewise:
$ escape "$(echo -ne "$escapedString")"
Should output the string escaped again, though not necessarily in the same way as before. E.g. \0134 may become \\ or vice versa.
Don't use echo -e -- it's very poorly specified in POSIX, and considered deprecated for all but the simplest uses. Bash has extensions to its printf that provide a better-supported approach:
printf -v escaped_string %q "$raw_string"
...gives you a shell-escaped string from a raw one (storing it in a variable named escaped_string), and
printf -v raw_string %b "$escaped_string"
...gives you a raw string from a backslash-escaped one, storing it in raw_string.
Note that the two escape syntaxes are not equivalent -- strings escaped with printf %q are ready for eval, rather than for printf %b.
That is, you can safely run:
eval "myvar=$escaped_string"
...when escaped_string has been created with printf %q as above.
That said: What's the use case? It's strongly preferred to handle raw strings as raw strings (using NUL terminaters when delimiting is necessary), rather than converting them to and from an escaped form.