Bash write to file without echo

Question

As an exercise  does a method exist to redirect a string to a file without echo  Currently I am using  echo  Hello world   gt  test txt   I know about cat and printf  I was thinking something like   gt  test txt  lt  lt  lt  Hello world    Of course this doesnt work  but maybe a similar command

User · Answer

I ve a solution for bash purists   The function  define  helps us to assign a multiline value to a variable  This one takes one positional parameter  the variable name to assign the value   In the heredoc  optionally there re parameter expansions too      bin bash  define        IFS    n  read -r -d     1    BUCH  Matth  us 1   define TEXT lt  lt EOT Aus dem Buch    BUCH   1 Buch des Geschlechts Jesu Christi  des Sohnes Davids  des Sohnes Abrahams  2 Abraham zeugte Isaak  Isaak aber zeugte Jakob  Jakob aber zeugte Juda und seine Br  der  3 Juda aber zeugte Phares und Zara von der Thamar  Phares aber zeugte Esrom  Esrom aber zeugte Aram   4 Aram aber zeugte Aminadab  Aminadab aber zeugte Nahasson  Nahasson aber zeugte Salmon  5 Salmon aber zeugte Boas von der Rahab  Boas aber zeugte Obed von der Ruth  Obed aber zeugte Isai  6 Isai aber zeugte David  den K  nig  David aber zeugte Salomon von der  die Urias Weib gewesen    EOT  define TEXTNOEXPAND lt  lt  EOT    or define TEXTNOEXPAND lt  lt  EOT  Aus dem Buch    BUCH   1 Buch des Geschlechts Jesu Christi  des Sohnes Davids  des Sohnes Abrahams  2 Abraham zeugte Isaak  Isaak aber zeugte Jakob  Jakob aber zeugte Juda und seine Br  der  3 Juda aber zeugte Phares und Zara von der Thamar  Phares aber zeugte Esrom  Esrom aber zeugte Aram    4 Aram aber zeugte Aminadab  Aminadab aber zeugte Nahasson  Nahasson aber zeugte Salmon  5 Salmon aber zeugte Boas von der Rahab  Boas aber zeugte Obed von der Ruth  Obed aber zeugte Isai  6 Isai aber zeugte David  den K  nig  David aber zeugte Salomon von der  die Urias Weib gewesen    EOT  OUTFILE   tmp matth  us eins     Create file  gt   OUTFILE     Write contents      printf   s n    TEXT     printf   s n    TEXTNOEXPAND     gt  gt   OUTFILE     Be lucky

User · Answer

I had the problem not being able to send     and ended up with echo   echo  Hello world    dd of test txt

User · Answer

You can do this with  cat  and a here-document   cat  lt  lt EOF  gt  test txt some text EOF   One reason for doing this would be to avoid any possibility of a password being visible in the output of ps   However  in bash and most modern shells   echo  is a built-in command and it won t show up in ps output  so using something like this is safe  ignoring any issues with storing passwords in files  of course    echo   password   gt  test txt

User · Answer

Interestingly  I had this problem too   so I search and found this thread    I found that this worked well for me  echo  quot Hello world quot    grep  quot  quot   gt  test txt  However - When I had closed that terminal and opened a new one  I discovered that the problem went away   I wish I had kept that terminal open to compare the settings   My current terminal is a bash shell  Not sure what caused that issue to begin with - anyone

User · Answer

There are way too many ways to possibly discuss that you probably don t care about  You can hack of course - strace bash  or do all sorts of black magic running Bash in gdb   You actually have two completely different examples there   lt  lt  lt  string  is already writing a string to a file  If anything is acceptable other than printf  echo  and cat  you can use many other commands to behave like cat  sed  awk  tee  etc      cp  dev stdin   tmpfooblah  lt  lt  lt  hello world   cat tmpfooblah hello world   Or hell  depending on how you ve compiled Bash     enable -f  usr lib bash print print  print  hello world   gt tmpfile   If you want to use only bash strings and redirection  in pure bash  with no hacking  and no loadables  it is not possible  In ksh93 however  it is possible      rm tmpfooblah   lt  lt  lt  hello world   gt tmpfooblah  lt      amp       cat tmpfooblah  hello world

User · Answer

There are multiple ways to do it  let s run this script called exercise sh     usr bin env bash   gt  file1 txt cat  lt  lt  lt   This is a here-string with random value  RANDOM     Or if you prefer to see what is happening and write to file as well tee file2 txt  lt  lt  lt   Here is another here-string I can see and write to file     if you want to work multiline easily cat  lt  lt EOF  gt  file3 txt You don t need to escape any quotes here    marks start of variables  unless escaped  This is random value from variable  RANDOM This is literal   RANDOM EOF    Let s say you have a variable with multiline text and you want to manipulate it a   1 2 3 33      Assume I want to have lines containing  3   Instead of grep it can even be another script a   echo   a    grep 3     Then you want to write this to a file  although here-string is fine    if you don t need single-liner command  prefer heredoc   Herestring   If it s single liner  variable needs to be quoted to preserve newlines   gt  file4 txt cat  lt  lt  lt    a    Heredoc cat  lt  lt EOF  gt  file5 txt  a EOF   This is the output you should see     bash exercise sh Here is another here-string I can see and write to file   And files should contain these     ls exercise sh  file1 txt  file2 txt  file3 txt  file4 txt  file5 txt   cat file1 txt This is a here-string with random value 20914   cat file2 txt Here is another here-string I can see and write to file   cat file3 txt You don t need to escape any quotes here    marks start of variables  unless escaped  This is random value from variable 15899 This is literal  RANDOM   cat file4 txt 3 33   cat file5 txt 3 33

User · Answer

awk   BEGIN   print  Hello  world       gt  test txt   would do it

User · Answer

The way to do this in bash is  zsh  lt  lt  lt    gt  test  lt  lt  lt   Hello World     This is one of the interesting differences between zsh and bash  given an unchained  gt  or  gt  gt   zsh has the good sense to hook it up to stdin  while bash does not   It would be downright useful - if it were only standard  I tried to use this to send  amp  append my ssh key over ssh to a remote authorized keys file  but the remote host was bash  of course  and quietly did nothing   And that s why you should just use cat

User · Answer

Only redirection won t work  since there s nothing to connect the now-open file descriptors  So no  there is no way like this

[bash] Bash write to file without echo?

Examples related to bash

Examples related to command-line

Examples related to io-redirection