Why doesn't the follow bash script work? I would like it to output
two lines like this:
XXXXXXX
YYYYYYY
It works if I change the sed line to use a filename instead of the variable, but I want to use the variable.
#!/bin/bash
input=$(echo -e '=======\n-------\n')
for sym in = -; do
if [ "$sym" == '-' ]; then
replace=Y
else
replace=X
fi
printf "%s\n" "s/./$replace/g"
done | sed -f- <<<"$input"
The main problem is that you're giving sed two sources to read standard input from: the for loop that is fed through the pipe, and the variable coming through the here-string. As it turns out, the here-string gets precedence and sed complains that there are extra characters after a command (= is a command).
Instead of a here-string, you could use process substitution:
for sym in = -; do
if [ "$sym" == '-' ]; then
replace=Y
else
replace=X
fi
printf "%s\n" "s/./$replace/g"
done | sed -f- <(printf '%s\n' '=======' '-------')
You'll notice that the output isn't what you want, though, namely
YYYYYYY
YYYYYYY
This is because the sed script you end up with looks like this:
s/./X/g
s/./Y/g
No matter what you do first, the last command replaces everything with Y.
Related
I'm relatively new to bash scripting and I would like someone to explain this properly, thank you. Here is my code:
#! /bin/bash
echo "first arg: $1"
echo "first arg: $2"
var="$( grep -rnw $1 -e $2 | cut -d ":" -f1 )"
var2=$( grep -rnw $1 -e $2 | cut -d ":" -f1 | awk '{print substr($0,length,1)}')
echo "$var"
echo "$var2"
The problem I have is with the output, the script I'm trying to write is a c++ function searcher, so upon launching my script I have 2 arguments, one for the directory and the second one as the function name. This is how my output looks like:
first arg: Projekt
first arg: iseven
Projekt/AX/include/ax.h
Projekt/AX/src/ax.cpp
h
p
Now my question is: how do can I save the line by line output as a variable, so that later on I can use var as a path, or to use var2 as a character to compare. My plan was to use IF() statements to determine the type, idea: IF(last_char == p){echo:"something"}What I've tried was this question: Capturing multiple line output into a Bash variable and then giving it an array. So my code looked like: "${var[0]}". Please explain how can I use my line output later on, as variables.
I'd use readarray to populate an array variable just in case there's spaces in your command's output that shouldn't be used as field separators that would end up messing up foo=( ... ). And you can use shell parameter expansion substring syntax to get the last character of a variable; no need for that awk bit in your var2:
#!/usr/bin/env bash
readarray -t lines < <(printf "%s\n" "Projekt/AX/include/ax.h" "Projekt/AX/src/ax.cpp")
for line in "${lines[#]}"; do
printf "%s\n%s\n" "$line" "${line: -1}" # Note the space before the -1
done
will display
Projekt/AX/include/ax.h
h
Projekt/AX/src/ax.cpp
p
I want to input multiple strings.
For example:
abc
xyz
pqr
and I want output like this (including quotes) in a file:
"abc","xyz","pqr"
I tried the following code, but it doesn't give the expected output.
NextEmail=","
until [ "a$NextEmail" = "a" ];do
echo "Enter next E-mail: "
read NextEmail
Emails="\"$Emails\",\"$NextEmail\""
done
echo -e $Emails
This seems to work:
#!/bin/bash
# via https://stackoverflow.com/questions/1527049/join-elements-of-an-array
function join_by { local IFS="$1"; shift; echo "$*"; }
emails=()
while read line
do
if [[ -z $line ]]; then break; fi
emails+=("$line")
done
join_by ',' "${emails[#]}"
$ bash vvuv.sh
my-email
another-email
third-email
my-email,another-email,third-email
$
With sed and paste:
sed 's/.*/"&"/' infile | paste -sd,
The sed command puts "" around each line; paste does serial pasting (-s) and uses , as the delimiter (-d,).
If input is from standard input (and not a file), you can just remove the input filename (infile) from the command; to store in a file, add a redirection at the end (> outfile).
If you can withstand a trailing comma, then printf can convert an array, with no loop required...
$ readarray -t a < <(printf 'abc\nxyx\npqr\n' )
$ declare -p a
declare -a a=([0]="abc" [1]="xyx" [2]="pqr")
$ printf '"%s",' "${a[#]}"; echo
"abc","xyx","pqr",
(To be fair, there's a loop running inside bash, to step through the array, but it's written in C, not bash. :) )
If you wanted, you could replace the final line with:
$ printf -v s '"%s",' "${a[#]}"
$ s="${s%,}"
$ echo "$s"
"abc","xyx","pqr"
This uses printf -v to store the imploded text into a variable, $s, which you can then strip the trailing comma off using Parameter Expansion.
Is there a way to conditionally pipe the output of a command through sed, in a bash script? Depending upon a script option, I either want to pipe the output of a long pipe through sed, or omit the pipe through sed. Currently I'm doing
if [ $pipeit ]; then
sed_args='/omit this line/d'
else
sed_args='/$^/d' # pass-thru (what's a better sed pass thru?)
fi
some_cmd | sed "$sed_args"
I would keep it as simple as:
if [ $pipeit ]; then
some_cmd | sed '/omit this line/d'
else
some_cmd
fi
Why should you call sed if you don't need it? Just for your information, a possible sed command that does not change the input would be sed -n p
Btw, if some_cmd is kind of a large beast and you want to avoid duplicating it, wrap it into a function.
By default sed prints all lines:
if [ $pipeit ]; then
sed_args='/omit this line/d'
else
sed_args="" # pass-thru
fi
some_cmd | sed "${sed_args}"
There is this other tested solution:
some_cmd | if [ $pipeit ]; then
sed "/omit this line/d"
else
sed ""
fi
cat could be used instead of the sed ""
Finally, a string can be built and executed using eval.
some_cmd='printf "foo\n\nbar\n"'
if [ $pipeit ]; then
conditional_pipe='| sed "/foo/d"'
else
conditional_pipe=""
fi
eval "${some_cmd}" "${conditional_pipe}"
If some_cmd is complex it migth be tricky to build a string that would behave as expected with eval.
----
First solution for history
Using an impossible match with sed would make it print all lines to stdout:
$ printf "foo\n\nbar\n" | sed "/./{/^$/d}"
foo
bar
/./ selects a line with at least one char.
/^$/ selects an empty line.
I'm trying to read file line by line in bash.
Every line has format as follows text|number.
I want to produce file with format as follows text,text,text etc. so new file would have just text from previous file separated by comma.
Here is what I've tried and couldn't get it to work :
FILENAME=$1
OLD_IFS=$IFSddd
IFS=$'\n'
i=0
for line in $(cat "$FILENAME"); do
array=(`echo $line | sed -e 's/|/,/g'`)
echo ${array[0]}
i=i+1;
done
IFS=$OLD_IFS
But this prints both text and number but in different format text number
here is sample input :
dsadadq-2321dsad-dasdas|4212
dsadadq-2321dsad-d22as|4322
here is sample output:
dsadadq-2321dsad-dasdas,dsadadq-2321dsad-d22as
What did I do wrong?
Not pure bash, but you could do this in awk:
awk -F'|' 'NR>1{printf(",")} {printf("%s",$1)}'
Alternately, in pure bash and without having to strip the final comma:
#/bin/bash
# You can get your input from somewhere else if you like. Even stdin to the script.
input=$'dsadadq-2321dsad-dasdas|4212\ndsadadq-2321dsad-d22as|4322\n'
# Output should be reset to empty, for safety.
output=""
# Step through our input. (I don't know your column names.)
while IFS='|' read left right; do
# Only add a field if it exists. Salt to taste.
if [[ -n "$left" ]]; then
# Append data to output string
output="${output:+$output,}$left"
fi
done <<< "$input"
echo "$output"
No need for arrays and sed:
while IFS='' read line ; do
echo -n "${line%|*}",
done < "$FILENAME"
You just have to remove the last comma :-)
Using sed:
$ sed ':a;N;$!ba;s/|[0-9]*\n*/,/g;s/,$//' file
dsadadq-2321dsad-dasdas,dsadadq-2321dsad-d22as
Alternatively, here is a bit more readable sed with tr:
$ sed 's/|.*$/,/g' file | tr -d '\n' | sed 's/,$//'
dsadadq-2321dsad-dasdas,dsadadq-2321dsad-d22as
Choroba has the best answer (imho) except that it does not handle blank lines and it adds a trailing comma. Also, mucking with IFS is unnecessary.
This is a modification of his answer that solves those problems:
while read line ; do
if [ -n "$line" ]; then
if [ -n "$afterfirst" ]; then echo -n ,; fi
afterfirst=1
echo -n "${line%|*}"
fi
done < "$FILENAME"
The first if is just to filter out blank lines. The second if and the $afterfirst stuff is just to prevent the extra comma. It echos a comma before every entry except the first one. ${line%|\*} is a bash parameter notation that deletes the end of a paramerter if it matches some expression. line is the paramter, % is the symbol that indicates a trailing pattern should be deleted, and |* is the pattern to delete.
my question seems to be general, but i can't find any answers.
In sed command, how can you replace the substitution pattern by a value returned by a simple bash function.
For instance, I created the following function :
function parseDates(){
#Some process here with $1 (the pattern found)
return "dateParsed;
}
and the folowing sed command :
myCatFile=`sed -e "s/[0-3][0-9]\/[0-1][0-9]\/[0-9][0-9]/& parseDates &\}/p" myfile`
I found that the caracter '&' represents the current pattern found, i'd like it to be passed to my bash function and the whole pattern to be substituted by the pattern found +dateParsed.
Does anybody have an idea ?
Thanks
you can use the "e" option in sed command like this:
cat t.sh
myecho() {
echo ">>hello,$1<<"
}
export -f myecho
sed -e "s/.*/myecho &/e" <<END
ni
END
you can see the result without "e":
cat t.sh
myecho() {
echo ">>hello,$1<<"
}
export -f myecho
sed -e "s/.*/myecho &/" <<END
ni
END
Agree with Glenn Jackman.
If you want to use bash function in sed, something like this :
sed -rn 's/^([[:digit:].]+)/`date -d #&`/p' file |
while read -r line; do
eval echo "$line"
done
My file here begins with a unix timestamp (e.g. 1362407133.936).
Bash function inside sed (maybe for other purposes):
multi_stdin(){ #Makes function accepet variable or stdin (via pipe)
[[ -n "$1" ]] && echo "$*" || cat -
}
sans_accent(){
multi_stdin "$#" | sed '
y/àáâãäåèéêëìíîïòóôõöùúûü/aaaaaaeeeeiiiiooooouuuu/
y/ÀÁÂÃÄÅÈÉÊËÌÍÎÏÒÓÔÕÖÙÚÛÜ/AAAAAAEEEEIIIIOOOOOUUUU/
y/çÇñÑߢÐð£Øø§µÝý¥¹²³ªº/cCnNBcDdLOoSuYyY123ao/
'
}
eval $(echo "Rogério Madureira" | sed -n 's#.*#echo & | sans_accent#p')
or
eval $(echo "Rogério Madureira" | sed -n 's#.*#sans_accent &#p')
Rogerio
And if you need to keep the output into a variable:
VAR=$( eval $(echo "Rogério Madureira" | sed -n 's#.*#echo & | desacentua#p') )
echo "$VAR"
do it step by step. (also you could use an alternate delimiter , such as "|" instead of "/"
function parseDates(){
#Some process here with $1 (the pattern found)
return "dateParsed;
}
value=$(parseDates)
sed -n "s|[0-3][0-9]/[0-1][0-9]/[0-9][0-9]|& $value &|p" myfile
Note the use of double quotes instead of single quotes, so that $value can be interpolated
I'd like to know if there's a way to do this too. However, for this particular problem you don't need it. If you surround the different components of the date with ()s, you can back reference them with \1 \2 etc and reformat however you want.
For instance, let's reverse 03/04/1973:
echo 03/04/1973 | sed -e 's/\([0-9][0-9]\)\/\([0-9][0-9]\)\/\([0-9][0-9][0-9][0-9]\)/\3\/\2\/\1/g'
sed -e 's#[0-3][0-9]/[0-1][0-9]/[0-9][0-9]#& $(parseDates &)#' myfile |
while read -r line; do
eval echo "$line"
done
You can glue together a sed-command by ending a single-quoted section, and reopening it again.
sed -n 's|[0-3][0-9]/[0-1][0-9]/[0-9][0-9]|& '$(parseDates)' &|p' datefile
However, in contrast to other examples, a function in bash can't return strings, only put them out:
function parseDates(){
# Some process here with $1 (the pattern found)
echo dateParsed
}