I am currently working on a script that loops through an input file, the input file has a format similar to an /etc/hosts file in Linux. For example, the input file would look something like this:
192.168.1.21 host1
192.168.1.17 host5
192.168.1.168 host9
192.168.1.3 host3
192.168.1.37 host4
The data from the input file would need to be added to another file (an already existing hosts file) but it would need to be sorted in alphabetical order.
The following code snippet shows how I coded my script.
#Assign parameters to variables
inputFile=$1
hostsFile=$2
while read line
do
#Extract data from input file
ipAddress=`echo $line | awk '{print $1}'`
hostName=`echo $line | awk '{print $2}'`
#Loop to add host to hostname file, maintaining alphabetical order
while read line
do
addHost=`echo $line | awk '{print $2}'`
if [[ $profileEntry < $deviceName ]]; then
#Add device in sorted alphabetical order
echo $ipAddress "\t" $hostName >> $hostsFile
break;
fi
done < $hostsFile
done < $inputFile
I am doing the string comparison but when I write to the file using the >> or > operators the output will be append to the end of the file. Is there any Linux ksh construct or other method that can be used in shell scripts that will allow me to insert lines of text in alphabetical order, as opposed to appending text to the end of a file.
What you're asking for is impossible: The OS itself has no way to do insertions (as opposed to replacements) of content in the middle of a file. Other than when O_APPEND is in effect, write() calls overwrite and replace any content immediately after the current position of the file pointer.
Write a new file from scratch, and rename it over the original you're trying to replace; this has the benefit of being an atomic operation:
#!/usr/bin/env ksh
inputFile=$1
hostsFile=$2
tempFile=$(mktemp "${hostsFile}.XXXXXX")
if sort -u -- "$inputFile" "$hostsFile" >"$tempFile"; then
mv -- "$tempFile" "$hostsFile" && exit
fi
rm -f -- "$tempFile"
Related
I have a timestamp in this format:
(normal_file.csv)
timestamp
19/02/2002
19/02/2002
19/02/2002
19/02/2002
19/02/2002
19/02/2002
The dates are usually uniform, however, there are files with irregular dates pattern such as this example:
(abnormal_file.csv)
timestamp
19/02/2002
19/02/2003
19/02/2005
19/02/2006
In my directory, there are hundreds of files that consist of normal.csv and abnormal.csv.
I want to write a bash or awk script that detect the dates pattern in all files of a directory. Files with abnormal.csv should be moved automatically to a new, separate directory (let's say dir_different/).
Currently, I have tried the following:
#!/bin/bash
mkdir dir_different
for FILE in *.csv;
do
# pipe 1: detect the changes in the line
# pipe 2: print the timestamp column (first column, columns are comma-separated)
awk '$1 != prev {print ; prev = $1}' < $FILE | awk -F , '{print $1}'
done
If the timestamp in a given file is normal, then only one single timestamp will be printed; but for abnormal files, multiple dates will be printed.
I am not sure how to separate the abnormal files from the normal files, and I have tried the following:
do
output=$(awk 'FNR==3{print $0}' $FILE)
echo ${output}
if [[ ${output} =~ ([[:space:]]) ]]
then
mv $FILE dir_different/
fi
done
Or is there an easier method to detect changes in lines and separate files that have different lines? Thank you for any suggestions :)
Assuming that none of your "normal" CSV files have trailing newlines this should do the separation just fine:
#!/bin/bash
mkdir -p dir_different
for FILE in *.csv;
do
if awk '{a[$1]++}END{if(length(a)<=2){exit 1}}' "$FILE" ; then
echo mv "$FILE" dir_different
fi
done
After a dry-run just get rid of the echo :)
Edit:
{a[$1]++} This bit creates an array a that gets the first field of each line as an index, and that gets incremented every time the same value is seen.
END{if(length(a)<=2){exit 1}} This checks how many elements are in the array. If there there are less than 3 (which should be the case if there's always the same date and we only get 1 header, 1 date) exit the processing with 1.
"$FILE" is part of the bash script, not awk, and I quoted your variable out of habit, should you ever have files w/ spaces in their names you'll see why :)
So, a "normal" file contains only two different lines:
timestamp
dd/mm/yyyy
Testing if a file is normal is thus as simple as:
[ $(sort -u file.csv | wc -l) -eq 2 ]
This leads to the following possible solution:
#!/usr/bin/env bash
mkdir -p dir_different
for FILE in *.csv;
do
if [ $(sort -u "$FILE" | wc -l) -ne 2 ] ; then
echo mv "$FILE" dir_different
fi
done
New to awk like commands. I have single text file holding SQL DDL's in below format.
DROP TABLE IF EXISTS $database.TABLE_A ;
...
...
DROP TABLE IF EXISTS $database.TABLE_B ;
...
...
Would like to split single file into multiple files as
TABLE_A.SQL
TABLE_B.SQL
TABLE_X.SQL
I am able to get the table names from single file with the help of below awk command. Still struggling to split and rename file with TABLE_X.SQL name.
awk 'FNR==1 {split($5,a,"."); print a[2]}' *.SQL
I am using Windows 10 DOS shell.
Finally I am able to acheive desired output with the help of below Shell script, which we can run in Windows bash shell ...
#!/bin/bash
#Split single file
awk '/DROP/{x="F"++i;}{print > x".TXT";}' $1
#Create output directory
mkdir -p ./_output
#Move file by chaning extention
for f in *.TXT ; do
newfilename=$(awk 'FNR==1 {split($5,a,"."); print a[2]}' "$f")
echo Processed $f ... new file is $newfilename".SQL" ...
mv $f ./_output/$newfilename".SQL"
done
Could you please try following.
awk '/DROP/{if(file){close(file)};match($0,/TABLE_[^ ]*/);file=substr($0,RSTART,RLENGTH)".SQL"} {print > (file)}' Input_file
awk -F "[. ]" '{print >($(NF-1)".SQL")}' file.sql
I'm sorry for my poor English, first.
I want to read a file (tel.txt) that contains many tel numbers (a number per line) and use that line to grep command to search about the specific number in the source file (another file)!
I wrote this code :
dir="/home/mujan/Desktop/data/ADSL_CDR_Text_Parts_A"
file="$dir/tel.txt"
datafile="$dir/ADSL_CDR_Like_Tct4_From_960501_to_97501_Part0.txt"
while IFS= read -r line
do
current="$line"
echo `grep -F $current "$datafile" >> output.txt`
done < $file
the tel file sample :
44001547
44001478
55421487
but that code returns nothing!
when I declare 'current' variable with literals it works correctly!
what happened?!
Your grep command is redirected to write its output to a file, so you don't see it on the terminal.
Anyway, you should probably be using the much simpler and faster
grep -Ff "$file" "$datafile"
Add | tee -a output.txt if you want to save the output to a file and see it at the same time.
echo `command` is a buggy and inefficient way to write command. (echo "`command`" would merely be inefficient.) There is no reason to capture standard output into a string just so that you can echo that string to standard output.
Why don't you search for the line var directly? I've done some tests, this script works on my linux (CentOS 7.x) with bash shell:
#!/bin/bash
file="/home/mujan/Desktop/data/ADSL_CDR_Text_Parts_A/tel.txt"
while IFS= read -r line
do
echo `grep "$line" /home/mujan/Desktop/data/ADSL_CDR_Text_Parts_A/ADSL_CDR_Like_Tct4_From_960501_to_97501_Part0.tx >> output.txt`
done < $file
Give it a try... It shows nothing on the screen since you're redirecting the output to the file output.txt so the matching results are saved there.
You should use file descriptors when reading with while loop.instead use for loop to avoid false re-directions
dir="/home/mujan/Desktop/data/ADSL_CDR_Text_Parts_A"
file="$dir/tel.txt"
datafile="$dir/ADSL_CDR_Like_Tct4_From_960501_to_97501_Part0.txt"
for line in `cat $file`
do
current="$line"
echo `grep -F $current "$datafile" >> output.txt`
done
I need to remove a specific line number from a file using a bash script.
I get the line number from the grep command with the -n option.
I cannot use sed for a variety of reasons, least of which is that it is not installed on all the systems this script needs to run on and installing it is not an option.
awk is out of the question because in testing, on different machines with different UNIX/Linux OS's (RHEL, SunOS, Solaris, Ubuntu, etc.), it gives (sometimes wildly) different results on each. So, no awk.
The file in question is just a flat text file, with one record per line, so nothing fancy needs to be done, except for remove the line by number.
If at all possible, I need to avoid doing something like extracting the contents of the file, not including the line I want gone, and then overwriting the original file.
Since you have grep, the obvious thing to do is:
$ grep -v "line to remove" file.txt > /tmp/tmp
$ mv /tmp/tmp file.txt
$
But it sounds like you don't want to use any temporary files - I assume the input file is large and this is an embedded system where memory and storage are in short supply. I think you ideally need a solution that edits the file in place. I think this might be possible with dd but haven't figured it out yet :(
Update - I figured out how to edit the file in place with dd. Also grep, head and cut are needed. If these are not available then they can probably be worked around for the most part:
#!/bin/bash
# get the line number to remove
rline=$(grep -n "$1" "$2" | head -n1 | cut -d: -f1)
# number of bytes before the line to be removed
hbytes=$(head -n$((rline-1)) "$2" | wc -c)
# number of bytes to remove
rbytes=$(grep "$1" "$2" | wc -c)
# original file size
fsize=$(cat "$2" | wc -c)
# dd will start reading the file after the line to be removed
ddskip=$((hbytes + rbytes))
# dd will start writing at the beginning of the line to be removed
ddseek=$hbytes
# dd will move this many bytes
ddcount=$((fsize - hbytes - rbytes))
# the expected new file size
newsize=$((fsize - rbytes))
# move the bytes with dd. strace confirms the file is edited in place
dd bs=1 if="$2" skip=$ddskip seek=$ddseek conv=notrunc count=$ddcount of="$2"
# truncate the remainder bytes of the end of the file
dd bs=1 if="$2" skip=$newsize seek=$newsize count=0 of="$2"
Run it thusly:
$ cat > file.txt
line 1
line two
line 3
$ ./grepremove "tw" file.txt
7+0 records in
7+0 records out
0+0 records in
0+0 records out
$ cat file.txt
line 1
line 3
$
Suffice to say that dd is a very dangerous tool. You can easily unintentionally overwrite files or entire disks. Be very careful!
Try ed. The here-document-based example below deletes line 2 from test.txt
ed -s test.txt <<!
2d
w
!
You can do it without grep using posix shell builtins which should be on any *nix.
while read LINE || [ "$LINE" ];do
case "$LINE" in
*thing_you_are_grepping_for*)continue;;
*)echo "$LINE";;
esac
done <infile >outfile
If n is the line you want to omit:
{
head -n $(( n-1 )) file
tail +$(( n+1 )) file
} > newfile
Given dd is deemed too dangerous for this in-place line removal, we need some other method where we have fairly fine-grained control over the file system calls. My initial urge is to write something in c, but while possible, I think that is a bit of overkill. Instead it is worth looking to common scripting (not shell-scripting) languages, as these typically have fairly low-level file APIs which map to the file syscalls in a fairly straightforward manner. I'm guessing this can be done using python, perl, Tcl or one of many other scripting language that might be available. I'm most familiar with Tcl, so here we go:
#!/bin/sh
# \
exec tclsh "$0" "$#"
package require Tclx
set removeline [lindex $argv 0]
set filename [lindex $argv 1]
set infile [open $filename RDONLY]
for {set lineNumber 1} {$lineNumber < $removeline} {incr lineNumber} {
if {[eof $infile]} {
close $infile
puts "EOF at line $lineNumber"
exit
}
gets $infile line
}
set bytecount [tell $infile]
gets $infile rmline
set outfile [open $filename RDWR]
seek $outfile $bytecount start
while {[gets $infile line] >= 0} {
puts $outfile $line
}
ftruncate -fileid $outfile [tell $outfile]
close $infile
close $outfile
Note on my particular box I have Tcl 8.4, so I had to load the Tclx package in order to use the ftruncate command. In Tcl 8.5, there is chan truncate which could be used instead.
You can pass the line number you want to remove and the filename to this script.
In short, the script does this:
open the file for reading
read the first n-1 lines
get the offset of the start of the next line (line n)
read line n
open the file with a new FD for writing
move the file location of the write FD to the offset of the start of line n
continue reading the remaining lines from the read FD and write them to the write FD until the whole read FD is read
truncate the write FD
The file is edited exactly in place. No temporary files are used.
I'm pretty sure this can be re-written in python or perl or ... if necessary.
Update
Ok, so in-place line removal can be done in almost-pure bash, using similar techniques to the Tcl script above. But the big caveat is that you need to have truncate command available. I do have it on my Ubuntu 12.04 VM, but not on my older Redhat-based box. Here is the script:
#!/bin/bash
n=$1
filename=$2
exec 3<> $filename
exec 4<> $filename
linecount=1
bytecount=0
while IFS="" read -r line <&3 ; do
if [[ $linecount == $n ]]; then
echo "omitting line $linecount: $line"
else
echo "$line" >&4
((bytecount += ${#line} + 1))
fi
((linecount++))
done
exec 3>&-
exec 4>&-
truncate -s $bytecount $filename
#### or if you can tolerate dd, just to do the truncate:
# dd of="$filename" bs=1 seek=$bytecount count=0
#### or if you have python
# python -c "open(\"$filename\", \"ab\").truncate($bytecount)"
I would love to hear of a more generic (bash-only?) way to do the partial truncate at the end and complete this answer. Of course the truncate can be done with dd as well, but I think that was already ruled out for my earlier answer.
And for the record this site lists how to do an in-place file truncation in many different languages - in case any of these could be used in your environment.
If you can indicate under which circumstances on which platform(s) the most obvious Awk script is failing for you, perhaps we can devise a workaround.
awk "NR!=$N" infile >outfile
If course, obtaining $N with grep just to feed it to Awk is pretty bass-ackwards. This will delete the line containing the first occurrence of foo:
awk '/foo/ { if (!p++) next } 1' infile >outfile
Based on Digital Trauma's answere, I found an improvement that just needs grep and echo, but no tempfile:
echo $(grep -v PATTERN file.txt) > file.txt
Depending on the kind of lines your file contains and whether your pattern requires a more complex syntax or not, you can embrace the grep command with double quotes:
echo "$(grep -v PATTERN file.txt)" > file.txt
(useful when deleting from your crontab)
How do I iterate through each line of a text file with Bash?
With this script:
echo "Start!"
for p in (peptides.txt)
do
echo "${p}"
done
I get this output on the screen:
Start!
./runPep.sh: line 3: syntax error near unexpected token `('
./runPep.sh: line 3: `for p in (peptides.txt)'
(Later I want to do something more complicated with $p than just output to the screen.)
The environment variable SHELL is (from env):
SHELL=/bin/bash
/bin/bash --version output:
GNU bash, version 3.1.17(1)-release (x86_64-suse-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.
cat /proc/version output:
Linux version 2.6.18.2-34-default (geeko#buildhost) (gcc version 4.1.2 20061115 (prerelease) (SUSE Linux)) #1 SMP Mon Nov 27 11:46:27 UTC 2006
The file peptides.txt contains:
RKEKNVQ
IPKKLLQK
QYFHQLEKMNVK
IPKKLLQK
GDLSTALEVAIDCYEK
QYFHQLEKMNVKIPENIYR
RKEKNVQ
VLAKHGKLQDAIN
ILGFMK
LEDVALQILL
One way to do it is:
while read p; do
echo "$p"
done <peptides.txt
As pointed out in the comments, this has the side effects of trimming leading whitespace, interpreting backslash sequences, and skipping the last line if it's missing a terminating linefeed. If these are concerns, you can do:
while IFS="" read -r p || [ -n "$p" ]
do
printf '%s\n' "$p"
done < peptides.txt
Exceptionally, if the loop body may read from standard input, you can open the file using a different file descriptor:
while read -u 10 p; do
...
done 10<peptides.txt
Here, 10 is just an arbitrary number (different from 0, 1, 2).
cat peptides.txt | while read line
do
# do something with $line here
done
and the one-liner variant:
cat peptides.txt | while read line; do something_with_$line_here; done
These options will skip the last line of the file if there is no trailing line feed.
You can avoid this by the following:
cat peptides.txt | while read line || [[ -n $line ]];
do
# do something with $line here
done
Option 1a: While loop: Single line at a time: Input redirection
#!/bin/bash
filename='peptides.txt'
echo Start
while read p; do
echo "$p"
done < "$filename"
Option 1b: While loop: Single line at a time:
Open the file, read from a file descriptor (in this case file descriptor #4).
#!/bin/bash
filename='peptides.txt'
exec 4<"$filename"
echo Start
while read -u4 p ; do
echo "$p"
done
This is no better than other answers, but is one more way to get the job done in a file without spaces (see comments). I find that I often need one-liners to dig through lists in text files without the extra step of using separate script files.
for word in $(cat peptides.txt); do echo $word; done
This format allows me to put it all in one command-line. Change the "echo $word" portion to whatever you want and you can issue multiple commands separated by semicolons. The following example uses the file's contents as arguments into two other scripts you may have written.
for word in $(cat peptides.txt); do cmd_a.sh $word; cmd_b.py $word; done
Or if you intend to use this like a stream editor (learn sed) you can dump the output to another file as follows.
for word in $(cat peptides.txt); do cmd_a.sh $word; cmd_b.py $word; done > outfile.txt
I've used these as written above because I have used text files where I've created them with one word per line. (See comments) If you have spaces that you don't want splitting your words/lines, it gets a little uglier, but the same command still works as follows:
OLDIFS=$IFS; IFS=$'\n'; for line in $(cat peptides.txt); do cmd_a.sh $line; cmd_b.py $line; done > outfile.txt; IFS=$OLDIFS
This just tells the shell to split on newlines only, not spaces, then returns the environment back to what it was previously. At this point, you may want to consider putting it all into a shell script rather than squeezing it all into a single line, though.
Best of luck!
A few more things not covered by other answers:
Reading from a delimited file
# ':' is the delimiter here, and there are three fields on each line in the file
# IFS set below is restricted to the context of `read`, it doesn't affect any other code
while IFS=: read -r field1 field2 field3; do
# process the fields
# if the line has less than three fields, the missing fields will be set to an empty string
# if the line has more than three fields, `field3` will get all the values, including the third field plus the delimiter(s)
done < input.txt
Reading from the output of another command, using process substitution
while read -r line; do
# process the line
done < <(command ...)
This approach is better than command ... | while read -r line; do ... because the while loop here runs in the current shell rather than a subshell as in the case of the latter. See the related post A variable modified inside a while loop is not remembered.
Reading from a null delimited input, for example find ... -print0
while read -r -d '' line; do
# logic
# use a second 'read ... <<< "$line"' if we need to tokenize the line
done < <(find /path/to/dir -print0)
Related read: BashFAQ/020 - How can I find and safely handle file names containing newlines, spaces or both?
Reading from more than one file at a time
while read -u 3 -r line1 && read -u 4 -r line2; do
# process the lines
# note that the loop will end when we reach EOF on either of the files, because of the `&&`
done 3< input1.txt 4< input2.txt
Based on #chepner's answer here:
-u is a bash extension. For POSIX compatibility, each call would look something like read -r X <&3.
Reading a whole file into an array (Bash versions earlier to 4)
while read -r line; do
my_array+=("$line")
done < my_file
If the file ends with an incomplete line (newline missing at the end), then:
while read -r line || [[ $line ]]; do
my_array+=("$line")
done < my_file
Reading a whole file into an array (Bash versions 4x and later)
readarray -t my_array < my_file
or
mapfile -t my_array < my_file
And then
for line in "${my_array[#]}"; do
# process the lines
done
More about the shell builtins read and readarray commands - GNU
More about IFS - Wikipedia
BashFAQ/001 - How can I read a file (data stream, variable) line-by-line (and/or field-by-field)?
Related posts:
Creating an array from a text file in Bash
What is the difference between thee approaches to reading a file that has just one line?
Bash while read loop extremely slow compared to cat, why?
Use a while loop, like this:
while IFS= read -r line; do
echo "$line"
done <file
Notes:
If you don't set the IFS properly, you will lose indentation.
You should almost always use the -r option with read.
Don't read lines with for
If you don't want your read to be broken by newline character, use -
#!/bin/bash
while IFS='' read -r line || [[ -n "$line" ]]; do
echo "$line"
done < "$1"
Then run the script with file name as parameter.
Suppose you have this file:
$ cat /tmp/test.txt
Line 1
Line 2 has leading space
Line 3 followed by blank line
Line 5 (follows a blank line) and has trailing space
Line 6 has no ending CR
There are four elements that will alter the meaning of the file output read by many Bash solutions:
The blank line 4;
Leading or trailing spaces on two lines;
Maintaining the meaning of individual lines (i.e., each line is a record);
The line 6 not terminated with a CR.
If you want the text file line by line including blank lines and terminating lines without CR, you must use a while loop and you must have an alternate test for the final line.
Here are the methods that may change the file (in comparison to what cat returns):
1) Lose the last line and leading and trailing spaces:
$ while read -r p; do printf "%s\n" "'$p'"; done </tmp/test.txt
'Line 1'
'Line 2 has leading space'
'Line 3 followed by blank line'
''
'Line 5 (follows a blank line) and has trailing space'
(If you do while IFS= read -r p; do printf "%s\n" "'$p'"; done </tmp/test.txt instead, you preserve the leading and trailing spaces but still lose the last line if it is not terminated with CR)
2) Using process substitution with cat will reads the entire file in one gulp and loses the meaning of individual lines:
$ for p in "$(cat /tmp/test.txt)"; do printf "%s\n" "'$p'"; done
'Line 1
Line 2 has leading space
Line 3 followed by blank line
Line 5 (follows a blank line) and has trailing space
Line 6 has no ending CR'
(If you remove the " from $(cat /tmp/test.txt) you read the file word by word rather than one gulp. Also probably not what is intended...)
The most robust and simplest way to read a file line-by-line and preserve all spacing is:
$ while IFS= read -r line || [[ -n $line ]]; do printf "'%s'\n" "$line"; done </tmp/test.txt
'Line 1'
' Line 2 has leading space'
'Line 3 followed by blank line'
''
'Line 5 (follows a blank line) and has trailing space '
'Line 6 has no ending CR'
If you want to strip leading and trading spaces, remove the IFS= part:
$ while read -r line || [[ -n $line ]]; do printf "'%s'\n" "$line"; done </tmp/test.txt
'Line 1'
'Line 2 has leading space'
'Line 3 followed by blank line'
''
'Line 5 (follows a blank line) and has trailing space'
'Line 6 has no ending CR'
(A text file without a terminating \n, while fairly common, is considered broken under POSIX. If you can count on the trailing \n you do not need || [[ -n $line ]] in the while loop.)
More at the BASH FAQ
I like to use xargs instead of while. xargs is powerful and command line friendly
cat peptides.txt | xargs -I % sh -c "echo %"
With xargs, you can also add verbosity with -t and validation with -p
This might be the simplest answer and maybe it don't work in all cases, but it is working great for me:
while read line;do echo "$line";done<peptides.txt
if you need to enclose in parenthesis for spaces:
while read line;do echo \"$line\";done<peptides.txt
Ahhh this is pretty much the same as the answer that got upvoted most, but its all on one line.
#!/bin/bash
#
# Change the file name from "test" to desired input file
# (The comments in bash are prefixed with #'s)
for x in $(cat test.txt)
do
echo $x
done
Here is my real life example how to loop lines of another program output, check for substrings, drop double quotes from variable, use that variable outside of the loop. I guess quite many is asking these questions sooner or later.
##Parse FPS from first video stream, drop quotes from fps variable
## streams.stream.0.codec_type="video"
## streams.stream.0.r_frame_rate="24000/1001"
## streams.stream.0.avg_frame_rate="24000/1001"
FPS=unknown
while read -r line; do
if [[ $FPS == "unknown" ]] && [[ $line == *".codec_type=\"video\""* ]]; then
echo ParseFPS $line
FPS=parse
fi
if [[ $FPS == "parse" ]] && [[ $line == *".r_frame_rate="* ]]; then
echo ParseFPS $line
FPS=${line##*=}
FPS="${FPS%\"}"
FPS="${FPS#\"}"
fi
done <<< "$(ffprobe -v quiet -print_format flat -show_format -show_streams -i "$input")"
if [ "$FPS" == "unknown" ] || [ "$FPS" == "parse" ]; then
echo ParseFPS Unknown frame rate
fi
echo Found $FPS
Declare variable outside of the loop, set value and use it outside of loop requires done <<< "$(...)" syntax. Application need to be run within a context of current console. Quotes around the command keeps newlines of output stream.
Loop match for substrings then reads name=value pair, splits right-side part of last = character, drops first quote, drops last quote, we have a clean value to be used elsewhere.
This is coming rather very late, but with the thought that it may help someone, i am adding the answer. Also this may not be the best way. head command can be used with -n argument to read n lines from start of file and likewise tail command can be used to read from bottom. Now, to fetch nth line from file, we head n lines, pipe the data to tail only 1 line from the piped data.
TOTAL_LINES=`wc -l $USER_FILE | cut -d " " -f1 `
echo $TOTAL_LINES # To validate total lines in the file
for (( i=1 ; i <= $TOTAL_LINES; i++ ))
do
LINE=`head -n$i $USER_FILE | tail -n1`
echo $LINE
done
#Peter: This could work out for you-
echo "Start!";for p in $(cat ./pep); do
echo $p
done
This would return the output-
Start!
RKEKNVQ
IPKKLLQK
QYFHQLEKMNVK
IPKKLLQK
GDLSTALEVAIDCYEK
QYFHQLEKMNVKIPENIYR
RKEKNVQ
VLAKHGKLQDAIN
ILGFMK
LEDVALQILL
Another way to go about using xargs
<file_name | xargs -I {} echo {}
echo can be replaced with other commands or piped further.
for p in `cat peptides.txt`
do
echo "${p}"
done