Re: [gentoo-dev] Re: evar_push/pop helpers
On Monday 17 June 2013 01:42:15 Mike Frysinger wrote:
On Sunday 02 June 2013 13:38:04 Steven J. Long wrote:
On Sat, Jun 01, 2013 at 11:03:20PM -0400, Mike Frysinger wrote:
+# is not specified, the var will be unset.
+evar_push_set() {
+ local var=$1
+ evar_push ${var}
+ case $# in
+ 1) unset ${var} ;;
+ 2) eval ${var}=\$2 ;;
I wish you wouldn't use eval for this. I know it's technically okay here,
or would be if you verified the parameter, but bash has printf -v for
this purpose:
interesting, i hadn't seen that before ... looks new to bash-3.1. /me
tucks that into his tool belt.
although it doesn't quite work in the edge case where the value is an empty
string. consider:
unset x
printf -v x ''
echo ${x+set}
that should show set, but it does not. i'll have to keep `eval ${var}=`
when the value we're setting is empty. or just keep the eval code since i
have to do eval anyways at that point.
i'll report it upstream to the bash guys.
looks like it can be worked around by doing:
printf -v x '%s' ''
which is arguably what we want anyways
-mike
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Re: [gentoo-dev] Re: evar_push/pop helpers
On Sunday 02 June 2013 13:38:04 Steven J. Long wrote:
On Sat, Jun 01, 2013 at 11:03:20PM -0400, Mike Frysinger wrote:
--- eutils.eclass 22 May 2013 05:10:29 - 1.421
+++ eutils.eclass 2 Jun 2013 03:00:46 -
@@ -146,6 +146,77 @@ estack_pop() {
eval unset ${__estack_name}\[${__estack_i}\]
}
Just in passing, one of the places you don't want nullglob messing things
up.
not sure what you mean. that escapes the [] so that bash doesn't accidentally
glob things. when the code actually executes, you don't need to escape
things.
touch f i d x
unset arr
declare -A arr
arr[f]=1234
arr[idx]=4321
echo ${arr[f]} ${arr[idx]}
__estack_name=arr
__estack_i=f
eval unset ${__estack_name}\[${__estack_i}\]
echo ${#arr[@]}
__estack_i=idx
eval unset ${__estack_name}\[${__estack_i}\]
echo ${#arr[@]}
seems to work
+# is not specified, the var will be unset.
+evar_push_set() {
+ local var=$1
+ evar_push ${var}
+ case $# in
+ 1) unset ${var} ;;
+ 2) eval ${var}=\$2 ;;
I wish you wouldn't use eval for this. I know it's technically okay here,
or would be if you verified the parameter, but bash has printf -v for this
purpose:
interesting, i hadn't seen that before ... looks new to bash-3.1. /me tucks
that into his tool belt.
although it doesn't quite work in the edge case where the value is an empty
string. consider:
unset x
printf -v x ''
echo ${x+set}
that should show set, but it does not. i'll have to keep `eval ${var}=`
when the value we're setting is empty. or just keep the eval code since i
have to do eval anyways at that point.
i'll report it upstream to the bash guys.
printf -v $1 '%s' $2 2/dev/null || die unable to set: '$1' to: '$2'
Note you should verify the variable name, ime, irrespective of a die on the
printf (or eval in sh.) It's much better feedback to the developer using
the routine.
i don't think it's worth it. if you screw up the name, it tends to be a one-
time cost, and the error shown is pretty clear as to where it's coming from.
printf -v also works with array members btw, if you do decide to extend in
that direction:
i don't think i will, but i probably can convert the other core stack code to
use this ...
+ : ${cnt:=bad}
+ [[ -n ${cnt//[0-9]} ]] die ${FUNCNAME}: first arg must be a
number: $*
+ ;;
Though a generic is_int function comes in much handier, ime.
yeah, and we have other code that wants this (a simple grep for 0-9 in eclass/
shows a bunch of hits)
- # Some people like to make dirs of patches w/out suffixes (vim)
+ # We have to force sorting to C so that the wildcard expansion
# is consistent #471666.
+ evar_push_set LC_COLLATE C
+ # Some people like to make dirs of patches w/out suffixes (vim).
set -- $1/*${EPATCH_SUFFIX:+.${EPATCH_SUFFIX}}
+ evar_pop
Have to say I'd just do this in a function adding to a locally-scoped
array, if it were me, eg local args; foo $1 $EPATCH_SUFFIX; set --
${args[@]}; unset args
foo() {
local LC_COLLATE=C
args=($1/*${2:+.$2})
}
since i plan on using these funcs in other places, using the existing api
keeps things simple
though I'd prefer it if EPATCH_SUFFIX were allowed to be a list,
personally.
wouldn't really make this any easier
-mike
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[gentoo-dev] Re: evar_push/pop helpers
On Sat, Jun 01, 2013 at 11:03:20PM -0400, Mike Frysinger wrote:
simple set of helpers to save/restore a variable in a limited section of code
you can see an example of it in action at the end of the file where i need to
tweak epatch (and no, doing `LC_COLLATE=C set -- ` does not work).
-mike
--- eutils.eclass 22 May 2013 05:10:29 - 1.421
+++ eutils.eclass 2 Jun 2013 03:00:46 -
@@ -146,6 +146,77 @@ estack_pop() {
eval unset ${__estack_name}\[${__estack_i}\]
}
Just in passing, one of the places you don't want nullglob messing things up.
+# @FUNCTION: evar_push
+# @USAGE: variable to save [more vars to save]
+# @DESCRIPTION:
+# This let's you temporarily modify a variable and then restore it (including
+# set vs unset semantics). Arrays are not supported at this time.
+#
+# For example:
+# @CODE
+#evar_push LC_ALL
+#export LC_ALL=C
+#... do some stuff that needs LC_ALL=C set ...
+#evar_pop
+#
+## You can also save/restore more than one var at a time
+#evar_push BUTTERFLY IN THE SKY
+#... do stuff with the vars ...
+#evar_pop # This restores just one var, SKY
+#... do more stuff ...
+#evar_pop 3 # This pops the remaining 3 vars
+# @CODE
+evar_push() {
+ local var val
+ for var ; do
+ [[ ${!var+set} == set ]] \
+ val=${!var} \
+ || val=${___ECLASS_ONCE_EUTILS}
+ estack_push evar ${var} ${val}
+ done
+}
+
+# @FUNCTION: evar_push_set
+# @USAGE: variable to save [new value to store]
+# @DESCRIPTION:
+# This is a handy shortcut to save and temporarily set a variable. If a
value
+# is not specified, the var will be unset.
+evar_push_set() {
+ local var=$1
+ evar_push ${var}
+ case $# in
+ 1) unset ${var} ;;
+ 2) eval ${var}=\$2 ;;
I wish you wouldn't use eval for this. I know it's technically okay here, or
would be
if you verified the parameter, but bash has printf -v for this purpose:
printf -v $1 '%s' $2 2/dev/null || die unable to set: '$1' to: '$2'
Note you should verify the variable name, ime, irrespective of a die on the
printf
(or eval in sh.) It's much better feedback to the developer using the routine.
Here's what we currently use in sh:
# lib_key_ok $input_name
# is the input name ok as a variable or key identifier
lib_key_ok(){
case $1 in
''|[![:alpha:]_]*|*[![:alnum:]_]*) return 1
;; *) return 0
esac
}
# lib_check_key foo bar..
# die if any param is not lib_key_ok
lib_check_key() {
local i
for i; do
lib_key_ok $i || die bad key: '$i'
done
}
So I'd probably just use: lib_key_ok $1 || die $FUNCNAME: bad varname: '$1'
in this context, or amend the check_key function to use:
.. || die ${FUNCNAME[1]}: bad key '$i'
- since you're working in bash by definition.
printf -v also works with array members btw, if you do decide to extend in that
direction:
$ set -- 'foo[2]' 'array madness'
$ printf -v $1 %s $2
$ echo '${foo[2]}'
'array madness'
And yeah, you can compose the variable name, eg:
set -- foo 'array 1' 1
printf -v $1${3:+[$3]} %s $2
echo '${foo[1]}'
So long as the developer using the routines knows about quoting, that works
fine.
(If they don't, you have bigger problems.)
+ *) die ${FUNCNAME}: incorrect # of args: $* ;;
+ esac
+}
+
+# @FUNCTION: evar_pop
+# @USAGE: [number of vars to restore]
+# @DESCRIPTION:
+# Restore the variables to the state saved with the corresponding
+# evar_push call. See that function for more details.
+evar_pop() {
+ local cnt=$1
might as well use: cnt=${1:-bad}
+ case $# in
+ 0) cnt=1 ;;
+ 1)
and lose this line.
+ : ${cnt:=bad}
+ [[ -n ${cnt//[0-9]} ]] die ${FUNCNAME}: first arg must be a
number: $*
+ ;;
Though a generic is_int function comes in much handier, ime.
is_int() {
[[ $1 $1 != *[^0-9]* ]]
}
1) is_int $1 || die ..
cnt=$1
(I tend to guard against 0? as well, as octal inputs tend to mess things up
later. I'm
sure you can see the case for sh.)
+ *) die ${FUNCNAME}: only accepts one arg: $* ;;
+ esac
+
+ local var val
+ while (( cnt-- )) ; do
+ estack_pop evar val || die ${FUNCNAME}: unbalanced push
+ estack_pop evar var || die ${FUNCNAME}: unbalanced push
+ [[ ${val} == ${___ECLASS_ONCE_EUTILS} ]] \
+ unset ${var} \
+ || eval ${var}=\${val}
again: printf -v $var %s $val
Though I'd rather this were in an if, so you can test for error better:
if [[ $val = $___ECLASS_ONCE_EUTILS ]]; then
unset $var 2/dev/null || die unable to unset: '$var'
else printf -v $var %s $val 2/dev/null
