Sometimes I use same foreach operation with different target files in csh.
If I can give foreach command in a single line, I could easily substitue the target file names to repeat the process.(I usually use `find . -name ...` for target files)
For the purpose of this question, let's assume I want to cat all the *.txt files.
$ foreach i (*.txt)
foreach? cat $i
foreach? end
I read https://unix.stackexchange.com/questions/32873/running-a-full-foreach-command and tried
alias disp 'echo "foreach i (*.txt)"; echo "cat "\$"i"; echo "end"; | /bin/csh'
when I type disp it gives me Invalid null command.
If I can do it in a single line, I could do !foreach:gs/\.c\>/.h/ (do the same replacing .c with .h).
How can I do it?
This method works for me:
printf 'foreach f ( 1 2 3 )\n echo $f \n end' | tcsh
There is no easy way to do the foreach in one line under tcsh.
However, by using alias, you may get something very close to your question.
alias disp 'foreach i (*.txt)\
cat $i\
end'
You can call disp in your terminal.
If you want to direct the result into a pipe, then echo `disp` | grep foobar.
Sometimes, we need to save the result first, before further processing: set foo=`disp`
For your first question, I don't know how to write this in .cshrc file directly.
But I will use another flexible way to do this.
1: Write a shell script:
/home/user/disp.sh (or any path you want)
#/bin/bash
for line in `find . -name "*.c"`; do
echo ""
cat "$line"
done
Or you only have csh shell:
#/bin/csh
foreach i (*.c)
echo $i
end
Add new alias command to the .cshrc file
alias disp /home/user/disp.sh
Reenter csh shell (or relogin)
csh
For your second question, I did it on the same disp.sh script
This example is written in bash shell script.
#/bin/bash
usage() { echo "Usage: $0 [-d <depth>] [-e <extension>]" 1>&2; exit 1; }
while getopts ":d:e:" o; do
case "${o}" in
d)
d=${OPTARG}
;;
e)
e=${OPTARG}
;;
*)
usage
;;
esac
done
shift $((OPTIND-1))
if [ -z "${d}" ] || [ -z "${e}" ]; then
usage
fi
for line in `find . -maxdepth ${d} -name "*.${e}"`; do
echo ""
cat "$line"
done
You can simply type disp -d 1 -e c to find all .c file in the current path.
(-d means the depth of the file which is started from current path, -e means extension of files)
I tried to find answer but it looks there is no way. Just use bash by simply changing shell.
% bash
$ for f in *txt; do echo $f; done
$ exit
%
Use bash -c:
$ bash -c 'for i in *.txt; do cat $i; done'
Related
I have a variable in my bash script whose value is something like this:
~/a/b/c
Note that it is unexpanded tilde. When I do ls -lt on this variable (call it $VAR), I get no such directory. I want to let bash interpret/expand this variable without executing it. In other words, I want bash to run eval but not run the evaluated command. Is this possible in bash?
How did I manage to pass this into my script without expansion? I passed the argument in surrounding it with double quotes.
Try this command to see what I mean:
ls -lt "~"
This is exactly the situation I am in. I want the tilde to be expanded. In other words, what should I replace magic with to make these two commands identical:
ls -lt ~/abc/def/ghi
and
ls -lt $(magic "~/abc/def/ghi")
Note that ~/abc/def/ghi may or may not exist.
If the variable var is input by the user, eval should not be used to expand the tilde using
eval var=$var # Do not use this!
The reason is: the user could by accident (or by purpose) type for example var="$(rm -rf $HOME/)" with possible disastrous consequences.
A better (and safer) way is to use Bash parameter expansion:
var="${var/#\~/$HOME}"
Due to the nature of StackOverflow, I can't just make this answer unaccepted, but in the intervening 5 years since I posted this there have been far better answers than my admittedly rudimentary and pretty bad answer (I was young, don't kill me).
The other solutions in this thread are safer and better solutions. Preferably, I'd go with either of these two:
Charle's Duffy's solution
Håkon Hægland's solution
Original answer for historic purposes (but please don't use this)
If I'm not mistaken, "~" will not be expanded by a bash script in that manner because it is treated as a literal string "~". You can force expansion via eval like this.
#!/bin/bash
homedir=~
eval homedir=$homedir
echo $homedir # prints home path
Alternatively, just use ${HOME} if you want the user's home directory.
Plagarizing myself from a prior answer, to do this robustly without the security risks associated with eval:
expandPath() {
local path
local -a pathElements resultPathElements
IFS=':' read -r -a pathElements <<<"$1"
: "${pathElements[#]}"
for path in "${pathElements[#]}"; do
: "$path"
case $path in
"~+"/*)
path=$PWD/${path#"~+/"}
;;
"~-"/*)
path=$OLDPWD/${path#"~-/"}
;;
"~"/*)
path=$HOME/${path#"~/"}
;;
"~"*)
username=${path%%/*}
username=${username#"~"}
IFS=: read -r _ _ _ _ _ homedir _ < <(getent passwd "$username")
if [[ $path = */* ]]; then
path=${homedir}/${path#*/}
else
path=$homedir
fi
;;
esac
resultPathElements+=( "$path" )
done
local result
printf -v result '%s:' "${resultPathElements[#]}"
printf '%s\n' "${result%:}"
}
...used as...
path=$(expandPath '~/hello')
Alternately, a simpler approach that uses eval carefully:
expandPath() {
case $1 in
~[+-]*)
local content content_q
printf -v content_q '%q' "${1:2}"
eval "content=${1:0:2}${content_q}"
printf '%s\n' "$content"
;;
~*)
local content content_q
printf -v content_q '%q' "${1:1}"
eval "content=~${content_q}"
printf '%s\n' "$content"
;;
*)
printf '%s\n' "$1"
;;
esac
}
How about this:
path=`realpath "$1"`
Or:
path=`readlink -f "$1"`
A safe way to use eval is "$(printf "~/%q" "$dangerous_path")". Note that is bash specific.
#!/bin/bash
relativepath=a/b/c
eval homedir="$(printf "~/%q" "$relativepath")"
echo $homedir # prints home path
See this question for details
Also, note that under zsh this would be as as simple as echo ${~dangerous_path}
Here is a ridiculous solution:
$ echo "echo $var" | bash
An explanation of what this command does:
create a new instance of bash, by... calling bash;
take the string "echo $var" and substitute $var with the value of the variable (thus after the substitution the string will contain the tilde);
take the string produced by step 2 and send it to the instance of bash created in step one, which we do here by calling echo and piping its output with the | character.
Basically the current bash instance we're running takes our place as the user of another bash instance and types in the command "echo ~..." for us.
Expanding (no pun intended) on birryree's and halloleo's answers: The general approach is to use eval, but it comes with some important caveats, namely spaces and output redirection (>) in the variable. The following seems to work for me:
mypath="$1"
if [ -e "`eval echo ${mypath//>}`" ]; then
echo "FOUND $mypath"
else
echo "$mypath NOT FOUND"
fi
Try it with each of the following arguments:
'~'
'~/existing_file'
'~/existing file with spaces'
'~/nonexistant_file'
'~/nonexistant file with spaces'
'~/string containing > redirection'
'~/string containing > redirection > again and >> again'
Explanation
The ${mypath//>} strips out > characters which could clobber a file during the eval.
The eval echo ... is what does the actual tilde expansion
The double-quotes around the -e argument are for support of filenames with spaces.
Perhaps there's a more elegant solution, but this is what I was able to come up with.
why not delve straight into getting the user's home directory with getent?
$ getent passwd mike | cut -d: -f6
/users/mike
I believe this is what you're looking for
magic() { # returns unexpanded tilde express on invalid user
local _safe_path; printf -v _safe_path "%q" "$1"
eval "ln -sf ${_safe_path#\\} /tmp/realpath.$$"
readlink /tmp/realpath.$$
rm -f /tmp/realpath.$$
}
Example usage:
$ magic ~nobody/would/look/here
/var/empty/would/look/here
$ magic ~invalid/this/will/not/expand
~invalid/this/will/not/expand
Here is the POSIX function equivalent of Håkon Hægland's Bash answer
expand_tilde() {
tilde_less="${1#\~/}"
[ "$1" != "$tilde_less" ] && tilde_less="$HOME/$tilde_less"
printf '%s' "$tilde_less"
}
2017-12-10 edit: add '%s' per #CharlesDuffy in the comments.
Here's my solution:
#!/bin/bash
expandTilde()
{
local tilde_re='^(~[A-Za-z0-9_.-]*)(.*)'
local path="$*"
local pathSuffix=
if [[ $path =~ $tilde_re ]]
then
# only use eval on the ~username portion !
path=$(eval echo ${BASH_REMATCH[1]})
pathSuffix=${BASH_REMATCH[2]}
fi
echo "${path}${pathSuffix}"
}
result=$(expandTilde "$1")
echo "Result = $result"
Simplest: replace 'magic' with 'eval echo'.
$ eval echo "~"
/whatever/the/f/the/home/directory/is
Problem: You're going to run into issues with other variables because eval is evil. For instance:
$ # home is /Users/Hacker$(s)
$ s="echo SCARY COMMAND"
$ eval echo $(eval echo "~")
/Users/HackerSCARY COMMAND
Note that the issue of the injection doesn't happen on the first expansion. So if you were to simply replace magic with eval echo, you should be okay. But if you do echo $(eval echo ~), that would be susceptible to injection.
Similarly, if you do eval echo ~ instead of eval echo "~", that would count as twice expanded and therefore injection would be possible right away.
For anyone's reference, a function to mimic python's os.path.expanduser() behavior (no eval usage):
# _expand_homedir_tilde ~/.vim
/root/.vim
# _expand_homedir_tilde ~myuser/.vim
/home/myuser/.vim
# _expand_homedir_tilde ~nonexistent/.vim
~nonexistent/.vim
# _expand_homedir_tilde /full/path
/full/path
And the function:
function _expand_homedir_tilde {
(
set -e
set -u
p="$1"
if [[ "$p" =~ ^~ ]]; then
u=`echo "$p" | sed 's|^~\([a-z0-9_-]*\)/.*|\1|'`
if [ -z "$u" ]; then
u=`whoami`
fi
h=$(set -o pipefail; getent passwd "$u" | cut -d: -f6) || exit 1
p=`echo "$p" | sed "s|^~[a-z0-9_-]*/|${h}/|"`
fi
echo $p
) || echo $1
}
Just to extend birryree's answer for paths with spaces: You cannot use the eval command as is because it seperates evaluation by spaces. One solution is to replace spaces temporarily for the eval command:
mypath="~/a/b/c/Something With Spaces"
expandedpath=${mypath// /_spc_} # replace spaces
eval expandedpath=${expandedpath} # put spaces back
expandedpath=${expandedpath//_spc_/ }
echo "$expandedpath" # prints e.g. /Users/fred/a/b/c/Something With Spaces"
ls -lt "$expandedpath" # outputs dir content
This example relies of course on the assumption that mypath never contains the char sequence "_spc_".
You might find this easier to do in python.
(1) From the unix command line:
python -c 'import os; import sys; print os.path.expanduser(sys.argv[1])' ~/fred
Results in:
/Users/someone/fred
(2) Within a bash script as a one-off - save this as test.sh:
#!/usr/bin/env bash
thepath=$(python -c 'import os; import sys; print os.path.expanduser(sys.argv[1])' $1)
echo $thepath
Running bash ./test.sh results in:
/Users/someone/fred
(3) As a utility - save this as expanduser somewhere on your path, with execute permissions:
#!/usr/bin/env python
import sys
import os
print os.path.expanduser(sys.argv[1])
This could then be used on the command line:
expanduser ~/fred
Or in a script:
#!/usr/bin/env bash
thepath=$(expanduser $1)
echo $thepath
Just use eval correctly: with validation.
case $1${1%%/*} in
([!~]*|"$1"?*[!-+_.[:alnum:]]*|"") ! :;;
(*/*) set "${1%%/*}" "${1#*/}" ;;
(*) set "$1"
esac&& eval "printf '%s\n' $1${2+/\"\$2\"}"
I have done this with variable parameter substitution after reading in the path using read -e (among others). So the user can tab-complete the path, and if the user enters a ~ path it gets sorted.
read -rep "Enter a path: " -i "${testpath}" testpath
testpath="${testpath/#~/${HOME}}"
ls -al "${testpath}"
The added benefit is that if there is no tilde nothing happens to the variable, and if there is a tilde but not in the first position it is also ignored.
(I include the -i for read since I use this in a loop so the user can fix the path if there is a problem.)
for some reason when the string is already quoted only perl saves the day
#val="${val/#\~/$HOME}" # for some reason does not work !!
val=$(echo $val|perl -ne 's|~|'$HOME'|g;print')
I think that
thepath=( ~/abc/def/ghi )
is easier than all the other solutions... or I am missing something? It works even if the path does not really exists.
Following find command.
find Work/Linux4/test/test/test_goal/spyglass_reports/clock-reset/Ac_coherency06/ -iname "Ac_coherency*.csv"
is working fine when run on shell.
But in perl script it return nothing.
#!/bin/bash
REPORT_DIR=$1
FIND_CMD=$2
echo "##";
echo $REPORT_DIR ;
echo $FIND_CMD ;
LIST_OF_CSV=$(find $REPORT_DIR $FIND_CMD)
echo $LIST_OF_CSV
if [ "X" == "X${LIST_OF_CSV}" ]; then
echo "No files Found for : '$FIND_CMD' in directory ";
echo " '$REPORT_DIR' " | sed -e 's;Work/.*/test_reports;Work/PLATFORM/test_reports;g';
echo;
exit 0;
fi
Output of script:
##
Work/$PLATFORM_SPECIES/test_reports/clock-reset/Ac_coherency06 -iname "Ac_coherency06*.csv"
No files Found for : '-iname "Ac_coherency06*.csv"' in directory 'Work/PLATFORM/test_reports/clock-reset/Ac_coherency06'
If you're allowing a list of find predicates to be passed, keep them in list form, one argument to find per argument to your script. As an example implemented in this manner:
#!/bin/bash
# read report_dir off the command line, and shift it from arguments
report_dir=$1; shift
# generate a version of report_dir for human consumption
re='Work/.*/test_reports'
replacement='Work/PLATFORM/test_reports'
if [[ $report_dir =~ $re ]]; then
report_dir_name=${report_dir//${BASH_REMATCH[0]}/$replacement}
else
report_dir_name=$report_dir
fi
# read results from find -- stored NUL-delimited -- into an array
# using NUL-delimited inputs ensure that even unusual filenames work correctly
declare -a list_of_csv
while IFS= read -r -d '' filename; do
list_of_csv+=( "$filename" )
done < <(find "$report_dir" '(' "$#" ')' -print0)
# Use the length of that array to determine whether we found contents
echo "Found ${#list_of_csv[#]} files" >&2
if (( ${#list_of_csv[#]} == 0 )); then
echo "No files found in $report_dir_name" >&2
fi
Here, shift consumes the first argument from your list, and "$#" refers to all the others that remain after that point. This means that the items you want to have passed as separate, individual arguments to find can (and must) be passed as separate, individual arguments to your script.
Thus, with usage yourscript "/path/to/report/dir" -name '*.txt', initially, $1 will be /path/to/report/dir, $2 will be -name, and $3 will be *.txt. However, after shift is run, $1 will be -name, and $2 will be *.txt; and "$#" will refer to both of those, each passed as a separate word.
For details on the use of a while read loop to read items off of a stream, see BashFAQ #001.
For details on the syntax used for bash-native string replacement, see BashFAQ #100 or http://wiki.bash-hackers.org/syntax/pe
For details on shell arrays, including ${#arrayname[#]} to check their length or "${arrayname[#]}" to expand to their contents, see BashFAQ #005.
If you have a command that is running well on the shell but not on your script, the first thing I would try would be to specify Bash on the command being called, see if this works:
bash -c 'find Work/Linux4/test/test/test_goal/spyglass_reports/clock-reset/Ac_coherency06/ -iname "Ac_coherency*.csv"'
Or even better:
/bin/bash -c 'find Work/Linux4/test/test/test_goal/spyglass_reports/clock-reset/Ac_coherency06/ -iname "Ac_coherency*.csv"'
You could also store the result on a variable or other data structure as needed, and pass it later to the script, for example:
ResultCommand="$(bash -c 'find Work/Linux4/test/test/test_goal/spyglass_reports/clock-reset/Ac_coherency06/ -iname "Ac_coherency*.csv"')"
Edit: this answer was edited more than once to fix possible issues.
I wrote a bash script that uploads a file on my home server. It gets activated from a folder action script using applescript. The setup is the folder on my desktop is called place_on_server. Its supposed to have an internal file structure exactly like the folder I want to write to: /var/www/media/
usage goes something like this:
if directory etc added to place_on_server: ./upload DIR etc
if directory of directory: etc/movies ./upload DIR etc movies //and so on
if file to place_on_server: ./upload F file.txt
if file in file in place_on_server ./upload F etc file.txt //and so on
for creating a directory its supposed to execute a command like:
ssh root#192.168.1.1<<EOF
cd /var/www/media/wherever
mkdir newdirectory
EOF
and for file placement:
rsync -rsh='ssh -p22' file root#192.168.1.1:/var/www/media/wherever
script:
#!/bin/bash
addr=$(ifconfig -a | ./test)
if ($# -le "1")
then
exit
elif ($1 -eq "DIR")
then
f1="ssh -b root#$addr<<EOF"
list = "cd /var/www/media\n"
if($# -eq "2")
then
list=list+"mkdir $2\nEOF\n"
else
num=2
i=$(($num))
while($num < $#)
do
i=$(($num))
list=list+"mkdir $i\n"
list=list+"cd $i\n"
$num=$num+1
done
fi
echo $list
elif ($1 -eq "F")
then
#list = "cd /var/www/media\n"
f2="rsync -rsh=\'ssh -p22\' "
f3 = "root#$addr:/var/www/media"
if($# -eq "2")
then
f2=f2+$2+" "+f3
else
num=3
i=$(($num))
while($num < $#)
do
i=$(($num))
f2=f2+"/"+$i
$num=$num+1
done
i=$(($num))
f2=f2+$i+" "+$f3
fi
echo $f2
fi
exit
output:
(prompt)$ ./upload2 F SO test.txt
./upload2: line 3: 3: command not found
./upload2: line 6: F: command not found
./upload2: line 25: F: command not found
So as you can see I'm having issues handling input. Its been awhile since I've done bash. And it was never extensive to begin with. Looking for a solution to my problem but also suggestions. Thanks in advance.
For comparisons, use [[ .. ]]. ( .. ) is for running commands in subshells
Don't use -eq for string comparisons, use =.
Don't use < for numerical comparisons, use -lt
To append values, f2="$f2$i $f3"
To add line feeds, use $'\n' outside of double quotes, or a literal linefeed inside of them.
You always need "$" on variables in strings to reference them, otherwise you get the literal string.
You can't use spaces around the = in assignments
You can't use $ before the variable name in assignments
To do arithmetics, use $((..)): result=$((var1+var2))
For indirect reference, such as getting $4 for n=4, use ${!n}
To prevent word splitting removing your line feeds, double quote variables such as in echo "$line"
Consider writing smaller programs and checking that they work before building out.
Here is how I would have written your script (slightly lacking in parameter checking):
#!/bin/bash
addr=$(ifconfig -a | ./test)
if [[ $1 = "DIR" ]]
then
shift
( IFS=/; echo ssh "root#$addr" mkdir -p "/var/www/media/$*"; )
elif [[ $1 = "F" ]]
then
shift
last=$#
file=${!last}
( IFS=/; echo rsync "$file" "root#$addr:/var/www/media/$*" )
else
echo "Unknown command '$1'"
fi
$* gives you all parameters separated by the first character in $IFS, and I used that to build the paths. Here's the output:
$ ./scriptname DIR a b c d
ssh root#somehost mkdir -p /var/www/media/a/b/c/d
$ ./scriptname F a b c d somefile.txt
rsync somefile.txt root#somehost:/var/www/media/a/b/c/d/somefile.txt
Remove the echos to actually execute.
The main problem with your script are the conditional statements, such as
if ($# -le "1")
Despite what this would do in other languages, in Bash this is essentially saying, execute the command line $# -le "1" in a subshell, and use its exit status as condition.
in your case, that expands to 3 -le "1", but the command 3 does not exist, which causes the error message
./upload2: line 3: 3: command not found
The closest valid syntax would be
if [ $# -le 1 ]
That is the main problem, there are other problems detailed and addressed in that other guy's post.
One last thing, when you're assigning value to a variable, e.g.
f3 = "root#$addr:/var/www/media"
don't leave space around the =. The statement above would be interpreted as "run command f3 with = and "root#$addr:/var/www/media" as arguments".
I have a file "a.txt", that contains file names with paths.
a.txt:
/root/chan/properties.lo
/root/attributes.cc
/root/chan/eagle/bath.ear
I would like to extract these file names and put them in one variable this way:
#!/bin/bash
for i in $(cat a.txt); do
o+=$(basename $i)
done
echo $o
But it does not work.
I am geting:
feedBackMailConfiguration.xmltiess
Please, help.
while read -r i;
do
o=$o" "$(basename $i)
done < a.txt
echo $o
The above will do it.
(edits for copy and paste errors)
More edits: just tried this (terminator, ubuntu) and it give the right result:
while read -r i; do o="$o $(basename $i)";done < a.txt
You just need to add a space concatenation to your script, like this:
#!/bin/bash
for i in $(cat a.txt); do
# Check the " " at the end of the following line
o+=$(basename $i)" "
done
echo $o
And it would work
"o+=..." is not really portable (which version of bash allows it? I never saw it until your mention of it? It looks like perl mechanisms)
Edit2 : following vladintok remarks on what the output is, I add DEBUG infos to try to pinpoints the problem
Edit3 : another step of trying to take out of the way every possible explanation for the weird output reported... I unalias, and unset any function named "o" and "basename" ...
Try:
#!/bin/bash
unalias o 2>/dev/null
unalias basename 2>/dev/null
unset o 2>/dev/null
unset basename 2>/dev/null
for i in $(cat a.txt); do
printf 'DEBUG: i is: %s\n' "$i"
o="${o} $(basename $i)"
done
printf 'DEBUG: final o is: %s\n' "$o"
echo $o
#end of the script.
(of course the above is a SINGLE file. Name it 'test.bash", make it executable: chmod +x test.bash, and then execute it : ./test.bash)
Edit1: I corrected the o=$o" "$(basename $i) into o="${o} $(basename $i)" as pointed out by Pantoine. Otherwise, toto=$toto" "titi : would assign to toto everything until the first space (which will be somewhere inside $toto, after the first iteration or if a basename contained spaces)...
This question has 3 parts, and each alone is easy, but combined together is not trivial (at least for me) :)
Need write a script what should take as its arguments:
one name of another command
several arguments for the command
list of files
Examples:
./my_script head -100 a.txt b.txt ./xxx/*.txt
./my_script sed -n 's/xxx/aaa/' *.txt
and so on.
Inside my script for some reason I need distinguish
what is the command
what are the arguments for the command
what are the files
so probably the most standard way write the above examples is:
./my_script head -100 -- a.txt b.txt ./xxx/*.txt
./my_script sed -n 's/xxx/aaa/' -- *.txt
Question1: Is here any better solution?
Processing in ./my_script (first attempt):
command="$1";shift
args=`echo $* | sed 's/--.*//'`
filenames=`echo $* | sed 's/.*--//'`
#... some additional processing ...
"$command" "$args" $filenames #execute the command with args and files
This solution will fail when the filenames will contain spaces and/or '--', e.g.
/some--path/to/more/idiotic file name.txt
Question2: How properly get $command its $args and $filenames for the later execution?
Question3: - how to achieve the following style of execution?
echo $filenames | $command $args #but want one filename = one line (like ls -1)
Is here nice shell solution, or need to use for example perl?
First of all, it sounds like you're trying to write a script that takes a command and a list of filenames and runs the command on each filename in turn. This can be done in one line in bash:
$ for file in a.txt b.txt ./xxx/*.txt;do head -100 "$file";done
$ for file in *.txt; do sed -n 's/xxx/aaa/' "$file";done
However, maybe I've misinterpreted your intent so let me answer your questions individually.
Instead of using "--" (which already has a different meaning), the following syntax feels more natural to me:
./my_script -c "head -100" a.txt b.txt ./xxx/*.txt
./my_script -c "sed -n 's/xxx/aaa/'" *.txt
To extract the arguments in bash, use getopts:
SCRIPT=$0
while getopts "c:" opt; do
case $opt in
c)
command=$OPTARG
;;
esac
done
shift $((OPTIND-1))
if [ -z "$command" ] || [ -z "$*" ]; then
echo "Usage: $SCRIPT -c <command> file [file..]"
exit
fi
If you want to run a command for each of the remaining arguments, it would look like this:
for target in "$#";do
eval $command \"$target\"
done
If you want to read the filenames from STDIN, it would look more like this:
while read target; do
eval $command \"$target\"
done
The $# variable, when quoted will be able to group parameters as they should be:
for parameter in "$#"
do
echo "The parameter is '$parameter'"
done
If given:
head -100 test this "File name" out
Will print
the parameter is 'head'
the parameter is '-100'
the parameter is 'test'
the parameter is 'this'
the parameter is 'File name'
the parameter is 'out'
Now, all you have to do is parse the loop out. You can use some very simple rules:
The first parameter is always the file name
The parameters that follow that start with a dash are parameters
After the "--" or once one doesn't start with a "-", the rest are all file names.
You can check to see if the first character in the parameter is a dash by using this:
if [[ "x${parameter}" == "x${parameter#-}" ]]
If you haven't seen this syntax before, it's a left filter. The # divides the two parts of the variable name. The first part is the name of the variable, and the second is the glob filter (not regular expression) to cut off. In this case, it's a single dash. As long as this statement isn't true, you know you have a parameter. BTW, the x may or may not be needed in this case. When you run a test, and you have a string with a dash in it, the test might mistake it for a parameter of the test and not the value.
Put it together would be something like this:
parameterFlag=""
for parameter in "$#" #Quotes are important!
do
if [[ "x${parameter}" == "x${parameter#-}" ]]
then
parameterFlag="Tripped!"
fi
if [[ "x${parameter}" == "x--" ]]
then
print "Parameter \"$parameter\" ends the parameter list"
parameterFlag="TRIPPED!"
fi
if [ -n $parameterFlag ]
then
print "\"$parameter\" is a file"
else
echo "The parameter \"$parameter\" is a parameter"
fi
done
Question 1
I don't think so, at least not if you need to do this for arbitrary commands.
Question 3
command=$1
shift
while [ $1 != '--' ]; do
args="$args $1"
shift
done
shift
while [ -n "$1" ]; do
echo "$1"
shift
done | $command $args
Question 2
How does that differ from question 3?