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213 lines
6.3 KiB
213 lines
6.3 KiB
# Copyright 1999-2017 Gentoo Foundation
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# Distributed under the terms of the GNU General Public License v2
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# @ECLASS: estack.eclass
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# @MAINTAINER:
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# base-system@gentoo.org
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# @BLURB: stack-like value storage support
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# @DESCRIPTION:
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# Support for storing values on stack-like variables.
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if [[ -z ${_ESTACK_ECLASS} ]]; then
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# @FUNCTION: estack_push
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# @USAGE: <stack> [items to push]
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# @DESCRIPTION:
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# Push any number of items onto the specified stack. Pick a name that
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# is a valid variable (i.e. stick to alphanumerics), and push as many
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# items as you like onto the stack at once.
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#
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# The following code snippet will echo 5, then 4, then 3, then ...
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# @CODE
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# estack_push mystack 1 2 3 4 5
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# while estack_pop mystack i ; do
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# echo "${i}"
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# done
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# @CODE
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estack_push() {
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[[ $# -eq 0 ]] && die "estack_push: incorrect # of arguments"
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local stack_name="_ESTACK_$1_" ; shift
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eval ${stack_name}+=\( \"\$@\" \)
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}
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# @FUNCTION: estack_pop
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# @USAGE: <stack> [variable]
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# @DESCRIPTION:
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# Pop a single item off the specified stack. If a variable is specified,
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# the popped item is stored there. If no more items are available, return
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# 1, else return 0. See estack_push for more info.
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estack_pop() {
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[[ $# -eq 0 || $# -gt 2 ]] && die "estack_pop: incorrect # of arguments"
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# We use the fugly _estack_xxx var names to avoid collision with
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# passing back the return value. If we used "local i" and the
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# caller ran `estack_pop ... i`, we'd end up setting the local
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# copy of "i" rather than the caller's copy. The _estack_xxx
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# garbage is preferable to using $1/$2 everywhere as that is a
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# bit harder to read.
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local _estack_name="_ESTACK_$1_" ; shift
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local _estack_retvar=$1 ; shift
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eval local _estack_i=\${#${_estack_name}\[@\]}
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# Don't warn -- let the caller interpret this as a failure
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# or as normal behavior (akin to `shift`)
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[[ $(( --_estack_i )) -eq -1 ]] && return 1
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if [[ -n ${_estack_retvar} ]] ; then
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eval ${_estack_retvar}=\"\${${_estack_name}\[${_estack_i}\]}\"
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fi
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eval unset \"${_estack_name}\[${_estack_i}\]\"
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}
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# @FUNCTION: evar_push
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# @USAGE: <variable to save> [more vars to save]
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# @DESCRIPTION:
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# This let's you temporarily modify a variable and then restore it (including
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# set vs unset semantics). Arrays are not supported at this time.
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#
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# This is meant for variables where using `local` does not work (such as
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# exported variables, or only temporarily changing things in a func).
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#
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# For example:
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# @CODE
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# evar_push LC_ALL
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# export LC_ALL=C
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# ... do some stuff that needs LC_ALL=C set ...
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# evar_pop
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#
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# # You can also save/restore more than one var at a time
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# evar_push BUTTERFLY IN THE SKY
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# ... do stuff with the vars ...
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# evar_pop # This restores just one var, SKY
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# ... do more stuff ...
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# evar_pop 3 # This pops the remaining 3 vars
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# @CODE
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evar_push() {
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local var val
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for var ; do
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[[ ${!var+set} == "set" ]] \
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&& val=${!var} \
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|| val="unset_76fc3c462065bb4ca959f939e6793f94"
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estack_push evar "${var}" "${val}"
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done
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}
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# @FUNCTION: evar_push_set
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# @USAGE: <variable to save> [new value to store]
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# @DESCRIPTION:
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# This is a handy shortcut to save and temporarily set a variable. If a value
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# is not specified, the var will be unset.
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evar_push_set() {
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local var=$1
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evar_push ${var}
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case $# in
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1) unset ${var} ;;
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2) printf -v "${var}" '%s' "$2" ;;
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*) die "${FUNCNAME}: incorrect # of args: $*" ;;
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esac
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}
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# @FUNCTION: evar_pop
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# @USAGE: [number of vars to restore]
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# @DESCRIPTION:
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# Restore the variables to the state saved with the corresponding
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# evar_push call. See that function for more details.
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evar_pop() {
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local cnt=${1:-bad}
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case $# in
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0) cnt=1 ;;
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1) isdigit "${cnt}" || die "${FUNCNAME}: first arg must be a number: $*" ;;
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*) die "${FUNCNAME}: only accepts one arg: $*" ;;
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esac
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local var val
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while (( cnt-- )) ; do
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estack_pop evar val || die "${FUNCNAME}: unbalanced push"
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estack_pop evar var || die "${FUNCNAME}: unbalanced push"
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[[ ${val} == "unset_76fc3c462065bb4ca959f939e6793f94" ]] \
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&& unset ${var} \
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|| printf -v "${var}" '%s' "${val}"
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done
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}
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# @FUNCTION: eshopts_push
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# @USAGE: [options to `set` or `shopt`]
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# @DESCRIPTION:
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# Often times code will want to enable a shell option to change code behavior.
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# Since changing shell options can easily break other pieces of code (which
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# assume the default state), eshopts_push is used to (1) push the current shell
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# options onto a stack and (2) pass the specified arguments to set.
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#
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# If the first argument is '-s' or '-u', we assume you want to call `shopt`
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# rather than `set` as there are some options only available via that.
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#
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# A common example is to disable shell globbing so that special meaning/care
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# may be used with variables/arguments to custom functions. That would be:
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# @CODE
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# eshopts_push -o noglob
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# for x in ${foo} ; do
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# if ...some check... ; then
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# eshopts_pop
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# return 0
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# fi
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# done
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# eshopts_pop
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# @CODE
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eshopts_push() {
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if [[ $1 == -[su] ]] ; then
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estack_push eshopts "$(shopt -p)"
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[[ $# -eq 0 ]] && return 0
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shopt "$@" || die "${FUNCNAME}: bad options to shopt: $*"
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else
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estack_push eshopts "$(shopt -p -o)"
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[[ $# -eq 0 ]] && return 0
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set "$@" || die "${FUNCNAME}: bad options to set: $*"
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fi
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}
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# @FUNCTION: eshopts_pop
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# @USAGE:
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# @DESCRIPTION:
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# Restore the shell options to the state saved with the corresponding
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# eshopts_push call. See that function for more details.
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eshopts_pop() {
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local s
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estack_pop eshopts s || die "${FUNCNAME}: unbalanced push"
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eval "${s}" || die "${FUNCNAME}: sanity: invalid shopt options: ${s}"
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}
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# @FUNCTION: eumask_push
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# @USAGE: <new umask>
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# @DESCRIPTION:
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# Set the umask to the new value specified while saving the previous
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# value onto a stack. Useful for temporarily changing the umask.
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eumask_push() {
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estack_push eumask "$(umask)"
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umask "$@" || die "${FUNCNAME}: bad options to umask: $*"
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}
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# @FUNCTION: eumask_pop
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# @USAGE:
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# @DESCRIPTION:
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# Restore the previous umask state.
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eumask_pop() {
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[[ $# -eq 0 ]] || die "${FUNCNAME}: we take no options"
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local s
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estack_pop eumask s || die "${FUNCNAME}: unbalanced push"
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umask ${s} || die "${FUNCNAME}: sanity: could not restore umask: ${s}"
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}
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# @FUNCTION: isdigit
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# @USAGE: <number> [more numbers]
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# @DESCRIPTION:
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# Return true if all arguments are numbers.
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isdigit() {
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local d
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for d ; do
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[[ ${d:-bad} == *[!0-9]* ]] && return 1
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done
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return 0
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}
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_ESTACK_ECLASS=1
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fi #_ESTACK_ECLASS
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