Daniel Veillard wrote:

On Wed, Apr 14, 2010 at 01:28:54PM +0200, Jim Meyering wrote:

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echo -e is not portable. This is the sole remaining use in all of libvirt.

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From a58cf340b5ebbca2157f43c6f23d4d6f56b848c7 Mon Sep 17 00:00:00 2001 From: Jim Meyering <meyering@redhat.com> Date: Wed, 14 Apr 2010 13:25:46 +0200 Subject: [PATCH] schematestutils.sh: improve shell portability: avoid "echo -e"

* tests/schematestutils.sh: Use printf rather than echo -e. --- tests/schematestutils.sh | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/tests/schematestutils.sh b/tests/schematestutils.sh index f172857..f2b3b50 100644 --- a/tests/schematestutils.sh +++ b/tests/schematestutils.sh @@ -22,7 +22,7 @@ do

test_result $n $(basename $(dirname $xml))"/"$(basename $xml) $ret if test "$verbose" = "1" && test $ret != 0 ; then - echo -e "$cmd\n$result" + printf '%s\n' "$cmd" "$result" fi if test "$ret" != 0 ; then f=`expr $f + 1`

I fail to see how printf(1) is any more portable than echo which is usually from the shell itself. Sounds to me that echo "$cmd" ; echo "$result" does what we want directly or am I mistaken ?

printf is most definitely more portable than "echo -e". Note that printf has been a shell built-in in just about every shell in common use for at least 10 years. Documentation everywhere has been telling developers to prefer "printf" over "echo-with-any-options" for nearly 20 years. Here's an excerpt from "info coreutils echo": POSIX does not require support for any options, and says that the behavior of `echo' is implementation-defined if any STRING contains a backslash or if the first argument is `-n'. Portable programs can use the `printf' command if they need to omit trailing newlines or output control characters or backslashes. *Note printf invocation::. While my objection was to "echo -e", plain 'echo "$var"' (where $var may be arbitrary) is not terribly reliable. There are plenty of caveats when using plain "echo". I.e., the first argument must not start with a "-". Using printf the way I do above, even if $cmd or $value starts with "-" or contains backslashes, it will be faithfully reproduced. However, if you use your pair of "echo" commands and some $result starts with "-", you'll get misleading output. Here's the section on "echo" in autoconf's "Limitations of Builtins" section: `echo' The simple `echo' is probably the most surprising source of portability troubles. It is not possible to use `echo' portably unless both options and escape sequences are omitted. Don't expect any option. Do not use backslashes in the arguments, as there is no consensus on their handling. For `echo '\n' | wc -l', the `sh' of Solaris outputs 2, but Bash and Zsh (in `sh' emulation mode) output 1. The problem is truly `echo': all the shells understand `'\n'' as the string composed of a backslash and an `n'. Within a command substitution, `echo 'string\c'' will mess up the internal state of ksh88 on AIX 6.1 so that it will print the first character `s' only, followed by a newline, and then entirely drop the output of the next echo in a command substitution. Because of these problems, do not pass a string containing arbitrary characters to `echo'. For example, `echo "$foo"' is safe only if you know that FOO's value cannot contain backslashes and cannot start with `-'. If this may not be true, `printf' is in general safer and easier to use than `echo' and `echo -n'. Thus, scripts where portability is not a major concern should use `printf '%s\n'' whenever `echo' could fail, and similarly use `printf %s' instead of `echo -n'. For portable shell scripts, instead, it is suggested to use a here-document like this: cat <<EOF $foo EOF Alternatively, M4sh provides `AS_ECHO' and `AS_ECHO_N' macros which choose between various portable implementations: `echo' or `print' where they work, `printf' if it is available, or else other creative tricks in order to work around the above problems.

Eric Blake wrote:

* tests/virt-aa-helper-test (testme): Use printf instead. --- tests/virt-aa-helper-test | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/virt-aa-helper-test b/tests/virt-aa-helper-test index 3a2e74b..910c438 100755 --- a/tests/virt-aa-helper-test +++ b/tests/virt-aa-helper-test @@ -112,10 +112,10 @@ testme() { fi fi

- echo -n " $outstr: " >$output - echo -n " '$extra_args $args" >$output + printf " $outstr: " >$output + printf " '$extra_args $args" >$output

These are fine if you know that the printf arguments never (and will never) contain the likes of "%" and "\". If you add a "%s" argument, then we don't even have to think about it: printf %s " $outstr: " >$output printf %s " '$extra_args $args" >$output

if [ -n "$input" ]; then - echo -n " < $input" >$output + printf " < $input" >$output fi echo "': " >$output set +e @@ -131,7 +131,7 @@ testme() { else echo "FAIL: exited with '$rc'" >$output echo "FAIL: exited with '$rc'" - echo -n " $outstr: " + printf " $outstr: " echo " '$extra_args $args': " errors=$(($errors + 1)) #exit $rc