>>>>> On Tue, 31 May 2022, Ionen Wolkens wrote: > +# @FUNCTION: esed > +# @USAGE: <sed-argument>... > +# @DESCRIPTION: > +# sed(1) wrapper that dies if the expression(s) did not modify any files. > +# sed's -i/--in-place is forced, and so stdin/out cannot be used.
This sounds like a simple enough task ...
> +esed() {
> + local -i i
> +
> + if [[ ${esedexps@a} =~ a ]]; then
> + # expression must be before -- but after the rest for e.g. -E
> to work
> + local -i pos
> + for ((pos=1; pos<=${#}; pos++)); do
> + [[ ${!pos} == -- ]] && break
> + done
> +
> + for ((i=0; i<${#esedexps[@]}; i++)); do
> + [[ ${esedexps[i]} ]] &&
> + esedexps= esed "${@:1:pos-1}" -e
> "${esedexps[i]}" "${@:pos}"
> + done
> +
> + unset esedexps
> + return 0
> + fi
> +
> + # Roughly attempt to find files in arguments by checking if it's a
> + # readable file (aka s/// is not a file) and does not start with -
> + # (unless after --), then store contents for comparing after sed.
> + local contents=() endopts files=()
> + for ((i=1; i<=${#}; i++)); do
> + if [[ ${!i} == -- && ! -v endopts ]]; then
> + endopts=1
> + elif [[ ${!i} =~ ^(-i|--in-place)$ && ! -v endopts ]]; then
> + # detect rushed sed -i -> esed -i, -i also silently
> breaks enewsed
> + die "passing ${!i} to ${FUNCNAME[0]} is invalid"
> + elif [[ ${!i} =~ ^(-f|--file)$ && ! -v endopts ]]; then
> + i+=1 # ignore script files
> + elif [[ ( ${!i} != -* || -v endopts ) && -f ${!i} && -r ${!i}
> ]]; then
> + files+=( "${!i}" )
> +
> + # eval 2>/dev/null to silence \0 warnings if sed binary
> files
> + eval 'contents+=( "$(<"${!i}")" )' 2>/dev/null \
> + || die "failed to read: ${!i}"
> + fi
> + done
> + (( ${#files[@]} )) || die "no readable files found from '${*}'
> arguments"
> +
> + local verbose
> + [[ ${ESED_VERBOSE} ]] && type diff &>/dev/null && verbose=1
> +
> + local changed newcontents
> + if [[ -v _esed_output ]]; then
> + [[ -v verbose ]] &&
> + einfo "${FUNCNAME[0]}: sed ${*} > ${_esed_output} ..."
> +
> + sed "${@}" > "${_esed_output}" \
> + || die "failed to run: sed ${*} > ${_esed_output}"
> +
> + eval 'newcontents=$(<${_esed_output})' 2>/dev/null \
> + || die "failed to read: ${_esed_output}"
> +
> + local IFS=$'\n' # sed concats with newline even if none at EOF
> + contents=${contents[*]}
> + unset IFS
> +
> + [[ ${contents} != "${newcontents}" ]] && changed=1
> +
> + [[ -v verbose ]] &&
> + diff -u --color --label="${files[*]}"
> --label="${_esed_output}" \
> + <(echo "${contents}") <(echo "${newcontents}")
> + else
> + [[ -v verbose ]] && einfo "${FUNCNAME[0]}: sed -i ${*} ..."
> +
> + sed -i "${@}" || die "failed to run: sed -i ${*}"
> +
> + for ((i=0; i<${#files[@]}; i++)); do
> + eval 'newcontents=$(<"${files[i]}")' 2>/dev/null \
> + || die "failed to read: ${files[i]}"
> +
> + if [[ ${contents[i]} != "${newcontents}" ]]; then
> + changed=1
> + [[ -v verbose ]] || break
> + fi
> +
> + [[ -v verbose ]] &&
> + diff -u --color --label="${files[i]}"{,} \
> + <(echo "${contents[i]}") <(echo
> "${newcontents}")
> + done
> + fi
> +
> + [[ -v changed ]] \
> + || die "no-op: ${FUNCNAME[0]} ${*}${_esed_command:+ (from:
> ${_esed_command})}"
> +}
... but then it's almost 100 lines of shell code, including very
convoluted parsing of parameters. The code for detection whether a
parameter is actually a file is a heuristic at best and looks rather
brittle. Also, don't use eval because it is evil.
So IMHO this isn't the right approach to the problem. If anything, make
it a simple function with well defined arguments, e.g. exactly one
expression and exactly one file, and call "sed -i" on it.
Then again, we had something similar in the past ("dosed" as a package
manager command) but later banned it for good reason.
Detection whether the file contents changed also seems complicated.
Why not compute a hash of the file before and after sed operated on it?
md5sum or even cksum should be good enough, since security isn't an
issue here.
Ulrich
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