How can I split a shell command over multiple lines when using an IF statement

Question

How can I split a command over multiple lines in the shell, when the command is part of an if statement?

This works:

if ! fab --fabfile=.deploy/fabfile.py --forward-agent --disable-known-hosts deploy:$target; then rc=1                                                                       
fi

This doesn't work:

# does not work:
if ! fab --fabfile=.deploy/fabfile.py \ 
  --forward-agent \
  --disable-known-hosts deploy:$target; then   
  rc=1
fi

Instead of the whole command executing, I get:

./script.sh: line 73: --forward-agent: command not found

More importantly, what is missing from my understanding of Bash that will help me understand this and similar issues in the future?

User · Answer

For Windows WSL Cygwin etc users   Make sure that your line endings are standard Unix line feeds  i e   n  LF  only   Using Windows line endings  r n  CRLF  line endings will break the command line break     This is because having   at the end of a line with Windows line ending translates to    r  n  As Mark correctly explains above      The line-continuation will fail if you have whitespace after the backslash and before the newline    This includes not just space    or tabs   t  but also the carriage return   r

User · Answer

The line-continuation will fail if you have whitespace  spaces or tab characters 1   after the backslash and before the newline  With no such whitespace  your example works fine for me    cat test sh if   fab --fabfile  deploy fabfile py      --forward-agent      --disable-known-hosts deploy  target  then      echo failed else      echo succeeded fi    alias fab true      test sh succeeded   alias fab false      test sh failed  Some detail promoted from the comments  the line-continuation backslash in the shell is not really a special case  it is simply an instance of the general rule that a backslash  quot quotes quot  the immediately-following character  preventing any special treatment it would normally be subject to  In this case  the next character is a newline  and the special treatment being prevented is terminating the command  Normally  a quoted character winds up included literally in the command  a backslashed newline is instead deleted entirely  But otherwise  the mechanism is the same  Most importantly  the backslash only quotes the immediately-following character  if that character is a space or tab  you just get a literal space or tab  and any subsequent newline remains unquoted   1  or carriage returns  for that matter  as Czechnology points out  Bash does not get along with Windows-formatted text files  not even in WSL  Or Cygwin  but at least their Bash port has added a set -o igncr option that you can set to make it carriage-return-tolerant

[syntax] How can I split a shell command over multiple lines when using an IF statement?

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