I am using sh shell script to read the files of a folder and display on the screen:
for d in `ls -1 $IMAGE_DIR | egrep "jpg$"`
do
pgm_file=$IMAGE_DIR/`echo $d | sed 's/jpg$/pgm/'`
echo "file $pgm_file";
done
the output result is reading line by line:
file file1.jpg
file file2.jpg
file file3.jpg
file file4.jpg
Because I am not familiar with this language, I would like to have the result that print first 2 results in the same row like this:
file file1.jpg; file file2.jpg;
file file3.jpg; file file4.jpg;
In other languages, I just put d++ but it does not work with this case.
Would this be doable? I will be happy if you would provide me sample code.
thanks in advance.
Let the shell do more work for you:
end_of_line=""
for d in "$IMAGE_DIR"/*.jpg
do
file=$( basename "$d" )
printf "file %s; %s" "$file" "$end_of_line"
if [[ -z "$end_of_line" ]]; then
end_of_line=$'\n'
else
end_of_line=""
fi
pgm_file=${d%.jpg}.pgm
# do something with "$pgm_file"
done
for d in "$IMAGE_DIR"/*jpg; do
pgm_file=${d%jpg}pgm
printf '%s;\n' "$d"
done |
awk 'END {
if (ORS != RS)
print RS
}
ORS = NR % n ? FS : RS
' n=2
Set n to whatever value you need.
If you're on Solaris, use nawk or /usr/xpg4/bin/awk
(do not use /usr/bin/awk).
Note also that I'm trying to use a standard shell syntax,
given your question is sh related (i.e. you didn't mention bash or ksh,
for example).
Something like this inside the loop:
echo -n "something; "
[[ -n "$oddeven" ]] && oddeven= || { echo;oddeven=x;}
should do.
Three per line would be something like
[[ "$((n++%3))" = 0 ]] && echo
(with n=1) before entering the loop.
Why use a loop at all? How about:
ls $IMAGE_DIR | egrep 'jpg$' |
sed -e 's/$/;/' -e 's/^/file /' -e 's/jpg$/pgm/' |
perl -pe '$. % 2 && chomp'
(The perl just deletes every other newline. You may want to insert a space and add a trailing newline if the last line is an odd number.)
Related
I have a textfile called log.txt, and it logs the file name and the path it was gotten from. so something like this
2.txt
/home/test/etc/2.txt
basically the file name and its previous location. I want to use grep to grab the file directory save it as a variable and move the file back to its original location.
for var in "$#"
do
if grep "$var" log.txt
then
# code if found
else
# code if not found
fi
this just prints out to the console the 2.txt and its directory since the directory has 2.txt in it.
thanks.
Maybe flip the logic to make it more efficient?
f=''
while read prev
do case "$prev" in
*/*) f="${prev##*/}"; continue;; # remember the name
*) [[ -e "$f" ]] && mv "$f" "$prev";;
done < log.txt
That walks through all the files in the log and if they exist locally, move them back. Should be functionally the same without a grep per file.
If the name is always the same then why save it in the log at all?
If it is, then
while read prev
do f="${prev##*/}" # strip the path info
[[ -e "$f" ]] && mv "$f" "$prev"
done < <( grep / log.txt )
Having the file names on the same line would significantly simplify your script. But maybe try something like
# Convert from command-line arguments to lines
printf '%s\n' "$#" |
# Pair up with entries in file
awk 'NR==FNR { f[$0]; next }
FNR%2 { if ($0 in f) p=$0; else p=""; next }
p { print "mv \"" p "\" \"" $0 "\"" }' - log.txt |
sh
Test it by replacing sh with cat and see what you get. If it looks correct, switch back.
Briefly, something similar could perhaps be pulled off with printf '%s\n' "$#" | grep -A 1 -Fxf - log.txt but you end up having to parse the output to pair up the output lines anyway.
Another solution:
for f in `grep -v "/" log.txt`; do
grep "/$f" log.txt | xargs -I{} cp $f {}
done
grep -q (for "quiet") stops the output
What I have is a file (let's call it 'xfile'), containing lines such as
file1 <- this line goes to file1
file2 <- this goes to file2
and what I want to do is run a script that does the work of actually taking the lines and writing them into the file.
The way I would do that manually could be like the following (for the first line)
(echo "this line goes to file1"; echo) >> file1
So, to automate it, this is what I tried to do
IFS=$'\n'
for l in $(grep '[a-z]* <- .*' xfile); do
$(echo $l | sed -e 's/\([a-z]*\) <- \(.*\)/(echo "\2"; echo)\>\>\1/g')
done
unset IFS
But what I get is
-bash: file1(echo "this content goes to file1"; echo)>>: command not found
-bash: file2(echo "this goes to file2"; echo)>>: command not found
(on OS X)
What's wrong?
This solves your problem on Linux
awk -F ' <- ' '{print $2 >> $1}' xfile
Take care in choosing field-separator in such a way that new files does not have leading or trailing spaces.
Give this a try on OSX
You can use the regex capabilities of bash directly. When you use the =~ operator to compare a variable to a regular expression, bash populates the BASH_REMATCH array with matches from the groups in the regex.
re='(.*) <- (.*)'
while read -r; do
if [[ $REPLY =~ $re ]]; then
file=${BASH_REMATCH[1]}
line=${BASH_REMATCH[2]}
printf '%s\n' "$line" >> "$file"
fi
done < xfile
I just want to read even line number from a file in bash shell, how to do it?
Also I just want to read the fifth line of a file, then how do it?
awk 'NR % 2 == 1' <filename>
For the second one:
awk 'NR == 5' <filename>
You can also use sed to get numbers in a specified range:
sed -ne '5,5p' <filename>
You could use the tail command. Put it in a for loop for the first case and the second is totally trivial if you get the first.
Or maybe you could even use awk:
awk NR==5 file_name
To read even number files using gnu-sed:
sed -n "2~2 p" file
To print specific line # from a file using sed:
sed '5q;d' file
Awk is often the answer (or, nowadays, Perl, Python etc. too)
If for some reason you must do it with only bash and the basic shell utilities:
cat file | \
while read line; do
i=$(( (i + 1) % 2 ))
if [[ $i -eq 0 ]]; then
echo $line // or whatever else you wanted to do with it
fi
done
And to get a specific line:
cat file | head -5 | tail -1
try this:
for example lines between 3 and 6
awk 'NR>=3 && NR<=6'`
These is a help to improve it(but not completed)
#!/bin/bash
test=`cat input.txt | awk 'NR>=3 && NR<=6'`
while read line; do
#do stuff
done <input.txt
This question already has answers here:
How to concatenate multiple lines of output to one line?
(12 answers)
Closed 4 years ago.
I have a file csv :
data1,data2,data2
data3,data4,data5
data6,data7,data8
I want to convert it to (Contained in a variable):
variable=data1,data2,data2%0D%0Adata3,data4,data5%0D%0Adata6,data7,data8
My attempt :
data=''
cat csv | while read line
do
data="${data}%0D%0A${line}"
done
echo $data # Fails, since data remains empty (loop emulates a sub-shell and looses data)
Please help..
Simpler to just strip newlines from the file:
tr '\n' '' < yourfile.txt > concatfile.txt
In bash,
data=$(
while read line
do
echo -n "%0D%0A${line}"
done < csv)
In non-bash shells, you can use `...` instead of $(...). Also, echo -n, which suppresses the newline, is unfortunately not completely portable, but again this will work in bash.
Some of these answers are incredibly complicated. How about this.
data="$(xargs printf ',%s' < csv | cut -b 2-)"
or
data="$(tr '\n' ',' < csv | cut -b 2-)"
Too "external utility" for you?
IFS=$'\n', read -d'\0' -a data < csv
Now you have an array! Output it however you like, perhaps with
data="$(tr ' ' , <<<"${data[#]}")"
Still too "external utility?" Well fine,
data="$(printf "${data[0]}" ; printf ',%s' "${data[#]:1:${#data}}")"
Yes, printf can be a builtin. If it isn't but your echo is and it supports -n, use echo -n instead:
data="$(echo -n "${data[0]}" ; for d in "${data[#]:1:${#data[#]}}" ; do echo -n ,"$d" ; done)"
Okay, now I admit that I am getting a bit silly. Andrew's answer is perfectly correct.
I would much prefer a loop:
for line in $(cat file.txt); do echo -n $line; done
Note: This solution requires the input file to have a new line at the end of the file or it will drop the last line.
Another short bash solution
variable=$(
RS=""
while read line; do
printf "%s%s" "$RS" "$line"
RS='%0D%0A'
done < filename
)
awk 'END { print r }
{ r = r ? r OFS $0 : $0 }
' OFS='%0D%0A' infile
With shell:
data=
while IFS= read -r; do
[ -n "$data" ] &&
data=$data%0D%0A$REPLY ||
data=$REPLY
done < infile
printf '%s\n' "$data"
Recent bash versions:
data=
while IFS= read -r; do
[[ -n $data ]] &&
data+=%0D%0A$REPLY ||
data=$REPLY
done < infile
printf '%s\n' "$data"
A very simple single-line solution which requires no extra files as its quite easy to understand (I think, just cat the file together and perform sed-replace):
output=$(echo $(cat ./myFile.txt) | sed 's/ /%0D%0A/g')
Useless use of cat, punished! You want to feed the CSV into the loop
while read line; do
# ...
done < csv
I have the following data in a Tab delimited file:
_ DATA _
Col1 Col2 Col3 Col4 Col5
blah1 blah2 blah3 4 someotherText
blahA blahZ blahJ 2 someotherText1
blahB blahT blahT 7 someotherText2
blahC blahQ blahL 10 someotherText3
I want to make sure that the data in 4th column of this file is always an integer. I know how to do this in perl
Read each line, Store value of 4th column in a variable
check if that variable is an integer
if above is true, continue the loop
else break out of the loop with message saying file data not correct
But how would I do this in a shell script using standard linux/unix filter? My guess would be to use grep, but I am not sure how?
cut -f4 data | LANG=C grep -q '[^0-9]' && echo invalid
LANG=C for speed
-q to quit at first error in possible long file
If you need to strip the first line then use tail -n+2 or you could get hacky and use:
cut -f4 data | LANG=C sed -n '1b;/[^0-9]/{s/.*/invalid/p;q}'
awk is the tool most naturally suited for parsing by columns:
awk '{if ($4 !~ /^[0-9]+$/) { print "Error! Column 4 is not an integer:"; print $0; exit 1}}' data.txt
As you get more complex with your error detection, you'll probably want to put the awk script in a file and invoke it with awk -f verify.awk data.txt.
Edit: in the form you'd put into verify.awk:
{
if ($4 !~/^[0-9]+$/) {
print "Error! Column 4 is not an integer:"
print $0
exit 1
}
}
Note that I've made awk exit with a non-zero code, so that you can easily check it in your calling script with something like this in bash:
if awk -f verify.awk data.txt; then
# action for success
else
# action for failure
fi
You could use grep, but it doesn't inherently recognize columns. You'd be stuck writing patterns to match the columns.
awk is what you need.
I can't upvote yet, but I would upvote Jefromi's answer if I could.
Sometimes you need it BASH only, because tr, cut & awk behave differently on Linux/Solaris/Aix/BSD/etc:
while read a b c d e ; do [[ "$d" =~ ^[0-9] ]] || echo "$a: $d not a numer" ; done < data
Edited....
#!/bin/bash
isdigit ()
{
[ $# -eq 1 ] || return 0
case $1 in
*[!0-9]*|"") return 0;;
*) return 1;;
esac
}
while read line
do
col=($line)
digit=${col[3]}
if isdigit "$digit"
then
echo "err, no digit $digit"
else
echo "hey, we got a digit $digit"
fi
done
Use this in a script foo.sh and run it like ./foo.sh < data.txt
See tldp.org for more info
Pure Bash:
linenum=1; while read line; do field=($line); if ((linenum>1)); then [[ ! ${field[3]} =~ ^[[:digit:]]+$ ]] && echo "FAIL: line number: ${linenum}, value: '${field[3]}' is not an integer"; fi; ((linenum++)); done < data.txt
To stop at the first error, add a break:
linenum=1; while read line; do field=($line); if ((linenum>1)); then [[ ! ${field[3]} =~ ^[[:digit:]]+$ ]] && echo "FAIL: line number: ${linenum}, value: '${field[3]}' is not an integer" && break; fi; ((linenum++)); done < data.txt
cut -f 4 filename
will return the fourth field of each line to stdout.
Hopefully that's a good start, because it's been a long time since I had to do any major shell scripting.
Mind, this may well not be the most efficient compared to iterating through the file with something like perl.
tail +2 x.x | sort -n -k 4 | head -1 | cut -f 4 | egrep "^[0-9]+$"
if [ "$?" == "0" ]
then
echo "file is ok";
fi
tail +2 gives you all but the first line (since your sample has a header)
sort -n -k 4 sorts the file numerically on the 4th column, letters will rise to the top.
head -1 gives you the first line of the file
cut -f 4 gives you the 4th column, of the first line
egrep "^[0-9]+$" checks if the value is a number (integers in this case).
If egrep finds nothing, $? is 1, otherwise it's 0.
There's also:
if [ `tail +2 x.x | wc -l` == `tail +2 x.x | cut -f 4 | egrep "^[0-9]+$" | wc -l` ] then
echo "file is ok";
fi
This will be faster, requiring two simple scans through the file, but it's not a single pipeline.
#OP, use awk
awk '$4+0<=0{print "not ok";exit}' file