Perhaps unsurprisingly,
Reviewed-by: David Mandelberg <da...@mandelberg.org>
On 2015-06-09 17:07, David Mandelberg wrote:
> From: Richard Hansen <rhan...@bbn.com>
>
> * add pecho(), a portable version of echo
> * use pecho() instead of echo for logging functions
> * add try() to make it easier to catch errors
> * have usage_fatal() send usage() output to stderr
> ---
> lib/util/shell_utils | 74
> +++++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 56 insertions(+), 18 deletions(-)
>
> diff --git a/lib/util/shell_utils b/lib/util/shell_utils
> index 8254a96..54a2f66 100644
> --- a/lib/util/shell_utils
> +++ b/lib/util/shell_utils
> @@ -1,25 +1,63 @@
> # Utility functions for shell scripts
>
> -warn () {
> - echo "WARNING:" "$@" >&2
> -}
> -
> -error () {
> - echo "ERROR:" "$@" >&2
> -}
> -
> -fatal () {
> - error "$@"
> - exit 1
> -}
> +# 'pecho': portable echo. POSIX says echo might interpret
> backslashes
> +# and a first argument that begins with '-', but printf is
> consistent.
> +# This function assumes that IFS is either unset or the first
> +# character of IFS is a space.
> +pecho() { printf %s\\n "$*"; }
> +
> +log() { pecho "$@"; }
> +warn() { log "WARNING: $@" >&2; }
> +error() { log "ERROR: $@" >&2; }
> +fatal() { error "$@"; exit 1; }
> +
> +# 'try': function to make it easier to catch errors
> +#
> +# 'set -e' is not clearly specified by POSIX, and different shells
> do
> +# very different things. Thus, it's not very useful for catching
> +# errors. 'try' is intended to be easy to use; usually you can just
> +# put it in front of a command, e.g.:
> +#
> +# try some_command --arg
> +#
> +# and it will cause the script to exit non-zero if the command
> fails.
> +#
> +# Caveats:
> +#
> +# * redirection errors aren't caught by 'try', so the following
> +# won't cause the script to exit:
> +#
> +# try echo foo >/no/such/directory/file
> +#
> +# you'll have to do this instead:
> +#
> +# try echo foo >/no/such/directory/file || exit 1
> +#
> +# or, to get an "ERROR: ..." message:
> +#
> +# try eval 'try echo foo >/no/such/directory/file'
> +#
> +# * the error message doesn't quote special characters in the
> +# arguments, which can lead to misleading error messages:
> +#
> +# $ try false "spaces and a single quote '"
> +# ERROR: 'false spaces and a single quote '' failed
> +#
> +# * the 'exit 1' in fatal() and try() only causes a subshell to
> +# exit, so if you're running something in a subshell you'll need
> +# to add '|| exit 1' after the subshell. For example:
> +#
> +# val=$(try some_command --arg) || exit 1
> +#
> +# note that POSIX allows the final stage in a pipeline to be in
> a
> +# subshell, so you'll need '|| exit 1' after pipelines too:
> +#
> +# pecho foo | try some_command --arg || exit 1
> +#
> +try() { "$@" || fatal "'$@' failed"; }
>
> # depends on the script defining a usage function that prints a help
> message
> -usage_fatal () {
> - error "$@"
> - echo >&2
> - usage
> - exit 1
> -}
> +usage_fatal() { error "$@"; pecho "" >&2; usage >&2; exit 1; }
>
>
> # Try to lock a mutex pathname.
--
David Eric Mandelberg / dseomn
http://david.mandelberg.org/
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