Appending a line break to an output file in a shell script

Question

I have a shell script that I am executing in Cygwin (maybe this is the problem). For this bit of code, I simply want to write the first line, and append a line break:

echo "`date` User `whoami` started the script." >> output.log
echo >> output.log

But the output.log file never seems to take the break. If I run the script multiple times, it's as if the second echo doesn't write to the file.

I've also tried:

echo -e "`date` User `whoami` started the script.\n" >> output.log

It yields the same results.

The odd thing is if I just enter the second echo statement above on the command line, without appending to the file, it gives me the expected output with the trailing line break.

Strange. How do you determine that the newlines are not added? — Michał Kosmulski, Mar 16 '12 at 17:03
Actually, I just looked at it seems the program I'm opening the log in is not interpreting the LF correctly, and is expecting Windows line breaks. If I cat the output, it seems to honor the breaks. — Ode, Mar 16 '12 at 18:41

score 37 · Accepted Answer · answered Mar 16 '12 at 17:05

37

I'm betting the problem is that Cygwin is writing Unix line endings (LF) to the file, and you're opening it with a program that expects Windows line-endings (CRLF). To determine if this is the case — and for a bit of a hackish workaround — try:

echo "`date` User `whoami` started the script."$'\r' >> output.log

(where the $'\r' at the end is an extra carriage-return; it, plus the Unix line ending, will result in a Windows line ending).

answered Mar 16 '12 at 17:05

ruakh

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This worked perfectly. The hypothesis about Unix vs Windows line endings seemed to be the problem – Ode Mar 16 '12 at 18:44

Daniel Haley · Answer 2 · 2012-03-16T17:12:54.837

24

Try:

echo "`date` User `whoami` started the script."$'\n' >> output.log

or just:

echo $'\n' >> output.log

edited Mar 16 '12 at 17:12

answered Mar 16 '12 at 17:02

Daniel Haley

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Note that command-substitution is not performed within `$'...'`, so that version will print the actual string, backticks and "date" and "whoami" and all, rather than running the `date` and `whoami` commands. – ruakh Mar 16 '12 at 17:07
@ruakh - Good catch. I did not notice that. I updated my answer. – Daniel Haley Mar 16 '12 at 17:12
1

The "$'\n' did not work, needed to do the "$'\r' from ruakh's solution. Thanks so much though! – Ode Mar 16 '12 at 18:44

score 5 · Answer 3 · edited Aug 08 '14 at 12:50

5

Try

echo -en "`date` User `whoami` started the script.\n" >> output.log

Try issuing this multiple times. I hope you are looking for the same output.

edited Aug 08 '14 at 12:50

brasofilo

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answered Aug 08 '14 at 10:07

Tanbir

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score 5 · Answer 4 · answered Dec 03 '20 at 12:08

5

this also works, and prolly is more readable than the echo version:

printf "`date` User `whoami` started the script.\r\n" >> output.log

answered Dec 03 '20 at 12:08

eadmaster

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score 3 · Answer 5 · edited May 25 '15 at 23:50

You can do that without an I/O redirection:

sed -i 's/$/\n/' filename

You can also use this command to append a newline to a list of files:

find dir -name filepattern | xargs sed -i 's/$/\n/' filename

For echo, some shells implement it as a shell builtin command. It might not accept the -e option. If you still want to use echo, try to find where the echo binary file is, using which echo. In most cases, it is located in /bin/echo, so you can use /bin/echo -e "\n" to echo a new line.

Appending a line break to an output file in a shell script

5 Answers5

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