I have variable x2 having 08PKj00000YdniC 09:59:04.53 (130409269)|SYSTEM_METHOD_EXIT||System.debug(ANY) ... many other lines from logs below I am trying to take the first line and discard everything else. When I execute echo $x2 | head -n 1 in terminal, I receive correct output 08PKj00000YdlM5 However, when I have an sh script and execute it from terminal like ./unwrap2.sh verbose I see strange result 08PKj00000YdniC 09:59:04.53 (130409269)|SYSTEM_METHOD_EXIT||System.debug(ANY) ... many other lines from logs below which looks like those lines are joined together even though I didn't expect this. What am I doing wrong inside a script and how can I fix this? Listing of unwrap2.sh shell script verbose=$1 # deploy data cloud Data Kit sf project deploy start -d dc # unwrap Data Kit components x=$(sf apex run -f scripts/unwrap.apex --json | jq '.result.logs' -r) x1=${x#*EXECUTION_STARTED} x2=${x1#*Result is \(success): } if [[ "$verbose" = "verbose" ]]; then echo "x2: $x2" fi x3=$(echo $x2 | head -n 1) if [[ "$verbose" = "verbose" ]]; then echo "x3: $x3" fi status=$(sf data query -q "select Id,Status FROM BackgroundOperation WHERE Id = '$x3'" --json | jq '.result.records.Status' -r) if [[ "$verbose" = "verbose" ]]; then echo "select Id,Status FROM BackgroundOperation WHERE Id = '$x3'" fi echo "Status: $status" while [[ "$status" != "Complete" ]]; do sleep 10 status=$(sf data query -q "select Id,Status FROM BackgroundOperation WHERE Id = '$x3'" --json | jq '.result.records.Status' -r) echo "Status: $status" done When I execute x3=$(echo $x2 | head -n 1) in terminal, it works fine.

So I'm a beginner and i have a project due next week. I have to print only the filename of the files that contain #!/bin/bash on the first line. So far I tried this head -n 1 $filename | grep -l "pattern" but when I execute it instead of the name of the files I receive (standard input) Like I said, I'm a beginner and so far I'm familiar with simple commands. So I would like to know where I f****** up and if there is a way of acheiving what I want without using harder commands like awk.

for fis in  find -perm -a+x -name "*.sh" -type f
do
head -n 1 $fis | grep -l "#!/bin/bash"
done

Here's a command to move all files whose *name* begin with 0 into a folder called zero : mv * zero **Question**: What is a command for moving all files whose *contents* begin with 0 into a folder called zero? Hopefully, there is a short command doing that also. I know that the first character of the contents of a file is given by head -c 1 filename.

Hello I would like to know if there is a way where I can only use head, tail, and pipes (and redirection eventually) to extract and output the start, middle characters, and end of a string Example: Given this string: SHOWpijfirefjTHISezpijSTRING, the command should output 'SHOWTHISSTRING' I tried something like (head -c 4 mdp > /dev/tty) | (tail -c +13 mdp | head -c 4 > /dev/tty) | (tail -c 6 mdp > /dev/tty) 2>&1 but it doesn't always return the same result and can give out of order results

I have to grab the first two lines, the lines 43 and 44, and the last 2 lines from a file in one conduct of commands. Is there away to print those while only using head, tail and pipe commands AND without special operators like && or ;? All I could think of is this (cat cool | head -n 2) | (tail -n +43 | head -n 2) | (tail -n 2) but it has cat... AND another option is (head -n 2 < cool) | (tail -n +43 < cool | head -n 2) | (tail -n 2 < cool) but for some reason it only shows the last line

I have this script that will show the user the head or tail of the files that are inside a set directory (currently that is set as ~/bin/new/*). This script works, but I would like to allow the user to not only show the head or the tail but so that they can select the directory. The current script is written as: while true;do echo "Would you like to list the head or tail?" read headortail if [[ $headortail = head ]]; then head -n 4 ~/bin/new/* break elif [[ $headortail = tail ]]; then tail -n 4 ~/bin/new/* break else echo "Invalid Input - Please Input head or tail" fi done If I add another line under the first echo such as: echo "Please type the directory" read dirLocation How could I implement this to the script? Would I do: head -n 4 $dirLocation Would that work?

When I run the command head -n 445 /etc/snort/snort.conf | nl I expect lines 1-445 to be returned. However, only up to line 371 is returned: [snip] 370 preprocessor dcerpc2_server: default, policy WinXP, \ 371 detect [smb [139, 445], tcp 35, udp 135, rpc-over-http-server 593], \ What is happening?

Say I have a huge text file (>2GB) and I just want to cat the lines X to Y (e.g. 57890000 to 57890010). From what I understand I can do this by piping head into tail or viceversa, i.e. head -A /path/to/file | tail -B or alternatively tail -C /path/to/file | head -D where A,B,C and D can be computed from the number of lines in the file, X and Y. But there are two problems with this approach: 1. You have to compute A,B,C and D. 2. The commands could pipe to each other **many more** lines than I am interested in reading (e.g. if I am reading just a few lines in the middle of a huge file) Is there a way to have the shell just work with and output the lines I want? (while providing only X and Y)?

Given the following 3 scripts: 1. `printf 'a\nb\nc\n' > file && { head -n 1; cat; } file && { head -n 1; cat; } $ printf 'a\nb\nc\n' | { head -n 1; cat; } a

$ { head -n 1; cat; } < <(printf 'a\nb\nc\n') a What is causing the different output from those scripts? --- Additional info - this is apparently not just a head problem: $ printf 'a\nb\nc\n' | { sed '1q'; cat; } a $ printf 'a\nb\nc\n' | { awk '1;{exit}'; cat; } a $ { sed '1q'; cat; } < <(printf 'a\nb\nc\n') a $ { awk '1;{exit}'; cat; } < <(printf 'a\nb\nc\n') a --- What would be a robust, POSIX way in shell (i.e. without just invoking awk or similar once to do everything) to read some number of lines from input and leave the rest for a different command regardless of whether the input is coming from a pipe or a file? --- This question was inspired by comments under an answer to [_sort the whole .csv based on the value in a certain column_](/a/750386/133219).

I have a directory with ~1M files and need to search for particular patterns. I know how to do it for all the files: find /path/ -exec grep -H -m 1 'pattern' \{\} \; The full output is not desired (too slow). Several first hits are OK, so I tried to limit number of the lines: find /path/ -exec grep -H -m 1 'pattern' \{\} \; | head -n 5 This results in 5 lines followed by find: `grep' terminated by signal 13 and find continues to work. This is well explained [here](https://superuser.com/a/554896/317607) . I tried quit action: find /path/ -exec grep -H -m 1 'pattern' \{\} \; -quit This outputs only the first match. Is it possible to limit find output with specific number of results (like providing an argument to quit similar to head -n)?

find command can output names of files as a null-delimited strings (if -print0 is provided), and xargs can consume them with -0 option turned on. But in between, it's hard to manipulate that collection of files - sort command has -z switch, that makes it possible to sort those files, but head and tail don't have them. How can I do head and tail on those null-delimited inputs in a convenient way? (I can always create a short & slow ruby script, but I hope that there could be a better way)

I often want to grep output from processes that include a few header lines. But if grep would remove all actual content lines, I don't want to display the header lines. For this to work I would need a command similar to tail but instead of only returning n lines, it would return *all* lines but only if there are at least n lines (the header). A colleague wrote a small Python tool to do this but it needs installation on all machines where I need to do this. Is there a short command line that can achieve this effect using a standard tool (maybe awk?) ?

I would like to round off the below numbers to nearest wholenumber using awk command and copy it to another column say col11 and col12. can anyone help eg 1) column5,column6,,,,,column11,column12, -21733.3, -4129.327,,,,,,, output expected column5,column6,,,,,column11,column12, -21733.3, -4129.327,,,,,-21733,-4129, 2) column5,column6,,,,,column11,column12, 21733.3,4129.327,,,,,,, output expected column5,column6,,,,,column11,column12, 21733.3,4129.327,,,,,21733,4129,

Is there a way to head/tail a document and get the reverse output; because you don't know how many lines there are in a document? I.e. I just want to get everything but the first 2 lines of foo.txt to append to another document.

Variants of this question have certainly been asked several times in different places, but I am trying to remove the last M lines from a file without luck. The second most voted answer in this question recommends doing the following to get rid of the last line in a file: head -n -1 foo.txt > temp.txt However, when I try that in OSX & Zsh, I get: head: illegal line count -- -1 Why is that? How can I remove the M **last** lines **and** the **first** N lines of a given file?

I am trying to write a shell script that can save the output of a piped process to a variable. This variable is then compared to a known string in order to discern whether or not my AT modem is connected to a network or not. My problem is when I run my script, the variable never matches the comparator no matter what I do. Minimal example attached. I ran my script in bash -x mode so I could track the variables along the script.

connected=$(echo -e 'AT+CREG?\r' > /dev/ttyUSB2 | head -2 /dev/ttyUSB2)
echo "\n"
compare=" $\'\r\' +CREG: $\'0,1\r"
echo "\n"
echo ${connected}
echo "\n"
if [ ${connected} = "${compare}" ] ; then
    echo "This may not be an AT&T card"
else 
    echo "Missed the if statement"
fi

**cat without -n** user@linux:~$ cat /etc/sysctl.conf | head -4 # # /etc/sysctl.conf - Configuration file for setting system variables # See /etc/sysctl.d/ for additional system variables. # See sysctl.conf (5) for information. user@linux:~$ There is -n option in cat command to display the line number of the file. user@linux:~$ cat -n /etc/sysctl.conf | head -4 1 # 2 # /etc/sysctl.conf - Configuration file for setting system variables 3 # See /etc/sysctl.d/ for additional system variables. 4 # See sysctl.conf (5) for information. user@linux:~$ user@linux:~$ cat -n /etc/sysctl.conf | tail -4 74 # Debian kernels have both set to 1 (restricted) 75 # See https://www.kernel.org/doc/Documentation/sysctl/fs.txt 76 #fs.protected_hardlinks=0 77 #fs.protected_symlinks=0 user@linux:~$ What about head and tail command? Is there any option to view the line number in head and tail without using cat -n and pipe the output to head or tail? I've tried head -n and tail -n but no line number displayed on the output. user@linux:~$ head -n4 /etc/sysctl.conf # # /etc/sysctl.conf - Configuration file for setting system variables # See /etc/sysctl.d/ for additional system variables. # See sysctl.conf (5) for information. user@linux:~$ user@linux:~$ tail -n4 /etc/sysctl.conf # Debian kernels have both set to 1 (restricted) # See https://www.kernel.org/doc/Documentation/sysctl/fs.txt #fs.protected_hardlinks=0 #fs.protected_symlinks=0 user@linux:~$

I am using a ffi for nodejs, which for the most part has nothing to do with this question, which is really about understanding pipes better, but does offer some context. function exec(cmd) { var buffer = new Buffer(32); var result = ''; var fp = libc.popen('( ' + cmd + ') 2>&1', 'r'); var code; if (!fp) throw new Error('execSync error: '+cmd); while( !libc.feof(fp) ){ libc.fgets(buffer, 32, fp) result += buffer.readCString(); } code = libc.pclose(fp) >> 8; return { stdout: result, code: code }; } which brings me to this bit of code that, when I run using this exec function tr -dc "[:alpha:]" < /dev/urandom | head -c ${1-8} I get the error: write error: Broken pipe tr: write error but I do get the output I expect: 8 random numbers. This confused the hell out of me but then in some wild googling I found this stack answer which perfectly fit my situation. I am left with some questions, though. Why does: tr -dc "[:alpha:]" < /dev/urandom | head -c ${1-8} throw a broken pipe error when called with my exec command but not when called from the shell? I don`t understand why when I call: tr -dc "[:alpha:]" < /dev/urandom it reads endlessly, but when I pipe it to: head -c ${1-8} It works without throwing a broken pipe error. It seems that head would take what it needs and tr would just read forever. At least it should throw broken pipe; head would consume the first 8 bytes and then tr would still be putting out output and broken pipe would be thrown by tr because head has stopped running. Both situations make sense to me, but it seems that they are some what exclusive to each other. I don't understand what is different between calling: exec(tr -dc "[:alpha:]" < /dev/urandom | head -c ${1-8}) and tr -dc "[:alpha:]" < /dev/urandom | head -c ${1-8} directly from the command line, and specifically why < an endless file into something and then | it to something makes it not run endlessly. I've been doing this for years and never questioned why it works this way. Lastly, is it OK to ignore this broken pipe error? Is there a way to fix it? Am I doing something wrong in my C++ ish javascript code? Am I missing some kind of popen basics? ------ EDIT messing around some more the code exec('head -10 /dev/urandom | tr -dc "[:alpha:]" | head -c 8') throws no pipe error!

In the example below, I have the right selection, but not the headers, and conversely. How can I have both? $ ps aux | grep 'gpart' erwann 200603 0.0 0.0 2608 72 pts/3 S 12:57 0:00 /bin/sh /usr/sbin/gparted root 200608 0.0 0.0 2608 1056 pts/3 S 12:57 0:00 /bin/sh /usr/sbin/gparted root 200693 0.0 0.0 2608 68 pts/3 S 12:57 0:00 /bin/sh /usr/lib/udisks2/udisks2-inhibit /usr/sbin/gpartedbin root 200700 1.9 0.2 264960 18620 pts/3 SLl 12:57 8:31 /usr/sbin/gpartedbin root 202327 99.8 0.0 2520 64 pts/3 R 13:36 400:07 gpart -s 512 /dev/sdc erwann 214723 0.0 0.0 9032 716 pts/4 S+ 20:17 0:00 grep --color=auto gpart $ ps aux | tee >(head -n1) >(grep 'gpart') > /dev/null USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND