Is it possible in bash to filter out a part of a string with another given string ?
I have a fixed list of motifs defined in a string. The order IS important and I want to keep only the parts that are passed as a parameter ?
myDefaultList="s,t,a,c,k" #order is important
toRetains="k,t,c,u" #provided by the user, order is not enforced
retained=filter $myDefaultList $toRetains # code to filter
echo $retained # will print t,c,k"
I can write an ugly method that will use IFS, arrays and loops, but I wonder if there's a 'clever' way to do that, using built-in commands ?
here is another approach
tolines() { echo $1 | tr ',' '\n'; }
grep -f <(tolines "$toRetains") <(tolines "$myDefaultList") | paste -sd,
will print
t,c,k
assign to a variable as usual.
Since you mention in your comments that you are open to sed/awk , check also this with GNU awk:
$ echo "$a"
s,t,a,c,k
$ echo "$b"
k,t,c,u
$ awk -v RS=",|\n" 'NR==FNR{a[$1];next}$1 in a{printf("%s%s",$1,RT)}' <(echo "$b") <(echo "$a")
t,c,k
#!/bin/bash
myDefaultList="s,t,a,c,k"
toRetains="s,t,c,u"
IFS=","
for i in $myDefaultList
do
echo $toRetains | grep $i > /dev/null
if [ "$?" -eq "0" ]
then
retained=$retained" "$i
fi
done
echo $retained | sed -e 's/ /,/g' -e 's/,//1'
I have checked it running for me. Kindly check.
Related
I have a variable foo.
echo "print foo" "$foo" ---> abc,bc,cde
I wanted to put quotes around each variable.
Expected result = 'abc','bc','cde'.
I have tried this way, but its not working:
join_lines() {
local IFS=${1:-,}
set --
while IFS= read -r line; do set -- "$#" "$'line'"; done
echo "$*"
}
Could you please try following, strictly written and tested with shown samples in GNU awk.
Without loop:
var="abc,bc,cde"
echo "$var" | awk -v s1="'" 'BEGIN{FS=",";OFS="\047,\047"} {$1=$1;$0=s1 $0 s1} 1'
With loop usual way to go through all fields(comma separated):
var="abc,bc,cde"
echo "$var" | awk -v s1="'" 'BEGIN{FS=OFS=","} {for(i=1;i<=NF;i++){$i=s1 $i s1}} 1'
Output will be 'abc','bc','cde'.
As alternative, using 'sed: replacing every 'with'', and adding ' at the beginning and end of the line to wrap the first/last tokens.
sed -e "s/^/'/" -e "s/$/'/" -e "s/,/','/g"
On surface, the question is on how to convert comma separated list of values (stored in a shell variable) into a comma separate list of quoted tokens. Extending the logic provided by OP, but using shell arrays
foo="abc,bc,cde"
IFS=, read -a items <<< "$foo"
result=
for r in "${items[#]}" ; do
[ "$result" ] && result+=","
result+="'$r'"
done
echo "RESULT=$result"
If needed, logic can be placed into a function/filter
function join_lines {
local -a items
local input result
while IFS=, read -a items ; do
result=
for r in "${items[#]}" ; do
[ "$result" ] && result+=","
result+="'$r'"
done
echo "$result"
done
}
I wrote what I thought was a quick script I could run on a bunch of machines. Instead it print what looks like might be directory contents in a recursive search:
version=$(mysql Varnish -B --skip-column-names -e "SELECT value FROM sys_param WHERE param='PatchLevel'" | sed -n 's/^.*\([0-9]\.[0-9]*\).*$/\1/p')
if [[ $(echo "if($version == 6.10) { print 1; } else { print 0; }" | bc) -eq 1 ]]; then
status=$(dpkg-query -l | awk '{print $2}' | grep 'sg-status-polling');
cons=$(dpkg-query -l | awk '{print $2}' | grep 'sg-consolidated-poller');
if [[ "$status" != "" && "$cons" != "" ]]; then
echo "about to change /var/www/Varnish/lib/Extra/SG/ObjectPoller2.pm"; echo;
cp /var/www/Varnish/lib/Extra/SG/ObjectPoller2.pm /var/www/Varnish/lib/Extra/SG/ObjectPoller2.pm.bkup;
sed -ir '184s!\x91\x93!\x91\x27--timeout=35\x27\x93!' /var/www/Varnish/lib/Extra/SG/ObjectPoller2.pm;
sed -n 183,185p /var/www/Varnish/lib/Extra/SG/ObjectPoller2.pm; echo;
else
echo "packages not found. Assumed to be not applicable";
fi
else
echo "This is 4.$version, skipping";
fi
The script is supposed to make sure Varnish is version 4.6.10 and has 2 custom .deb packages installed (not through apt-get). then makes a backup and edits a single line in a perl module from [] to ['--timeout=35']
it looks like its tripping up on the sed replace one liner.
There are two major problems (minor ones addressed in comments). The first is that you use the decimal code for [] instead of the hexa, so you should use \x5b\x5d instead of \x91\x93. The second problem is that if you do use the proper codes, sed will still interpret those syntactically as []. So you can't escape escaping. Here's what you should call:
sed -ri'.bkup' '184s!\[\]![\x27--timeout=35\x27]!' /var/www/Varnish/lib/Extra/SG/ObjectPoller2.pm
And this will create the backup for you (but you should double check).
Suppose I have a Unix shell variable as below
variable=abc,def,ghij
I want to extract all the values (abc, def and ghij) using a for loop and pass each value into a procedure.
The script should allow extracting arbitrary number of comma-separated values from $variable.
Not messing with IFS
Not calling external command
variable=abc,def,ghij
for i in ${variable//,/ }
do
# call your procedure/other scripts here below
echo "$i"
done
Using bash string manipulation http://www.tldp.org/LDP/abs/html/string-manipulation.html
You can use the following script to dynamically traverse through your variable, no matter how many fields it has as long as it is only comma separated.
variable=abc,def,ghij
for i in $(echo $variable | sed "s/,/ /g")
do
# call your procedure/other scripts here below
echo "$i"
done
Instead of the echo "$i" call above, between the do and done inside the for loop, you can invoke your procedure proc "$i".
Update: The above snippet works if the value of variable does not contain spaces. If you have such a requirement, please use one of the solutions that can change IFS and then parse your variable.
If you set a different field separator, you can directly use a for loop:
IFS=","
for v in $variable
do
# things with "$v" ...
done
You can also store the values in an array and then loop through it as indicated in How do I split a string on a delimiter in Bash?:
IFS=, read -ra values <<< "$variable"
for v in "${values[#]}"
do
# things with "$v"
done
Test
$ variable="abc,def,ghij"
$ IFS=","
$ for v in $variable
> do
> echo "var is $v"
> done
var is abc
var is def
var is ghij
You can find a broader approach in this solution to How to iterate through a comma-separated list and execute a command for each entry.
Examples on the second approach:
$ IFS=, read -ra vals <<< "abc,def,ghij"
$ printf "%s\n" "${vals[#]}"
abc
def
ghij
$ for v in "${vals[#]}"; do echo "$v --"; done
abc --
def --
ghij --
I think syntactically this is cleaner and also passes shell-check linting
variable=abc,def,ghij
for i in ${variable//,/ }
do
# call your procedure/other scripts here below
echo "$i"
done
#/bin/bash
TESTSTR="abc,def,ghij"
for i in $(echo $TESTSTR | tr ',' '\n')
do
echo $i
done
I prefer to use tr instead of sed, becouse sed have problems with special chars like \r \n in some cases.
other solution is to set IFS to certain separator
Another solution not using IFS and still preserving the spaces:
$ var="a bc,def,ghij"
$ while read line; do echo line="$line"; done < <(echo "$var" | tr ',' '\n')
line=a bc
line=def
line=ghij
Here is an alternative tr based solution that doesn't use echo, expressed as a one-liner.
for v in $(tr ',' '\n' <<< "$var") ; do something_with "$v" ; done
It feels tidier without echo but that is just my personal preference.
The following solution:
doesn't need to mess with IFS
doesn't need helper variables (like i in a for-loop)
should be easily extensible to work for multiple separators (with a bracket expression like [:,] in the patterns)
really splits only on the specified separator(s) and not - like some other solutions presented here on e.g. spaces too.
is POSIX compatible
doesn't suffer from any subtle issues that might arise when bash’s nocasematch is on and a separator that has lower/upper case versions is used in a match like with ${parameter/pattern/string} or case
beware that:
it does however work on the variable itself and pop each element from it - if that is not desired, a helper variable is needed
it assumes var to be set and would fail if it's not and set -u is in effect
while true; do
x="${var%%,*}"
echo $x
#x is not really needed here, one can of course directly use "${var%%:*}"
if [ -z "${var##*,*}" ] && [ -n "${var}" ]; then
var="${var#*,}"
else
break
fi
done
Beware that separators that would be special characters in patterns (e.g. a literal *) would need to be quoted accordingly.
Here's my pure bash solution that doesn't change IFS, and can take in a custom regex delimiter.
loop_custom_delimited() {
local list=$1
local delimiter=$2
local item
if [[ $delimiter != ' ' ]]; then
list=$(echo $list | sed 's/ /'`echo -e "\010"`'/g' | sed -E "s/$delimiter/ /g")
fi
for item in $list; do
item=$(echo $item | sed 's/'`echo -e "\010"`'/ /g')
echo "$item"
done
}
Try this one.
#/bin/bash
testpid="abc,def,ghij"
count=`echo $testpid | grep -o ',' | wc -l` # this is not a good way
count=`expr $count + 1`
while [ $count -gt 0 ] ; do
echo $testpid | cut -d ',' -f $i
count=`expr $count - 1 `
done
I have this file:
CLUSTERS=SP1,SP2,SP3
FNAME_SP1="REWARDS_BTS_SP1_<GTS>.dat"
FNAME_SP2="DUMP_LOG_SP2_<GTS>.dat"
FNAME_SP3="TEST_CASE_TABLE_SP3_<GTS>.dat"
What I want to get from these are:
REWARDS_BTS_SP1_
DUMP_LOG_SP2_
TEST_CASE_TABLE_SP3_
I loop through the CLUSTERS field, get the values, and use it to find the appropriate FNAME_<CLUSTERNAME> value. Basically, the CLUSTERS value are ALWAYS before the _<GTS> part of the string. Any string pattern will do, provided that the CLUSTERS value come before the _<GTS> at the end of the string.
Any suggestions? Here's a part of the script.
function loadClusters() {
for i in `echo ${!CLUSTER*}`
do
CLUSTER=`echo ${i} | grep $1`
if [[ -n ${CLUSTER} ]]; then
CLUSTER=${!i}
break;
fi
done
echo -e ${CLUSTER}
}
function loadClustersCampaign() {
for i in `echo ${!BPOINTS*}`
do
BPOINTS=`echo ${i} | grep $1`
if [[ -n ${BPOINTS} ]]; then
BPOINTS=${!i}
break;
fi
done
for i in `echo ${!FNAME*}`
do
FNAME=`echo ${i} | grep $1`
if [[ -n ${FNAME} ]]; then
FNAME=${!i}
break;
fi
done
echo -e ${BPOINTS}"|"${FNAME}
}
#get clusters
clusters=$(loadClusters $1)
for i in `echo $clusters | sed 's/,/ /g'`
do
file=$(loadClustersCampaign ${i/-/_} | awk -F"|" '{print $2}') ;
echo $file;
#then get the part of the $file variable
done
Fun with Shell Parameter Expansions
You can use matching-prefix notation and indirect expansion to get at the variables you want, and use the "remove suffix" expansion on each result to collect just the portions of the filename that you want. For example:
FNAME_SP1='REWARDS_BTS_SP1_<GTS>.dat'
FNAME_SP2='DUMP_LOG_SP2_<GTS>.dat'
FNAME_SP3='TEST_CASE_TABLE_SP3_<GTS>.dat'
for cluster in "${!FNAME_SP#}"; do
echo ${!cluster%%<GTS>*}
done
This will print out the following:
REWARDS_BTS_SP1_
DUMP_LOG_SP2_
TEST_CASE_TABLE_SP3_
but you could issue any valid shell command inside the loop instead of using echo.
See Also
http://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html
If you like an awk solution for this ,may be below will be useful.
> echo 'FNAME_SP1="REWARDS_BTS_SP1_<GTS>.dat"' | awk -F"<GTS>" '{split($1,a,"=\"");print substr(a[2],2)}'
REWARDS_BTS_SP1_
Furthur more detail below:
> cat temp
LUSTERS=SP1,SP2,SP3
FNAME_SP1="REWARDS_BTS_SP1_<GTS>.dat"
FNAME_SP2="DUMP_LOG_SP2_<GTS>.dat"
FNAME_SP3="TEST_CASE_TABLE_SP3_<GTS>.dat"
> awk -F"<GTS>" '/FNAME_SP/{split($1,a,"=");print substr(a[2],2)}' temp
REWARDS_BTS_SP1_
DUMP_LOG_SP2_
TEST_CASE_TABLE_SP3_
>
I cannot get this to work. I only want to get the string between 2 others in bash. Like this:
FOUND=$(echo "If show <start>THIS WORK<end> then it work" | **the magic**)
echo $FOUND
It seems so simple...
sed -n 's/.*<start>\(.*\)<end>.*/\1/p'
This can be done in bash without any external commands such as awk and sed. When doing a regex match in bash, the results of the match are put into a special array called BASH_REMATCH. The second element of this array contains the match from the first capture group.
data="If show <start>THIS WORK<end> then it work"
regex="<start>(.*)<end>"
[[ $data =~ $regex ]] && found="${BASH_REMATCH[1]}"
echo $found
This can also be done using perl regex in grep (GNU specific):
found=$(grep -Po '(?<=<start>).*(?=<end>)' <<< "If show <start>THIS WORK<end> then it work")
echo "$found"
If you have < start > and < end > in your string then this will work. Set the FS to < and >.
[jaypal:~/Temp] FOUND=$(echo "If show <start>THIS WORK<end> then it work" |
awk -v FS="[<>]" '{print $3}')
[jaypal:~/Temp] echo $FOUND
THIS WORK