grep for special characters in Unix

Question

I have a log file  application log  which might contain the following string of normal  amp  special characters on multiple lines      Q amp    amp     amp        amp   amp    amp   amp    I want to search for the line number s  which contains this special character string   grep     Q amp    amp     amp        amp   amp    amp   amp   application log   The above command doesn t return any results   What would be the correct syntax to get the line numbers

User · Accepted Answer

Tell grep to treat your input as fixed string using -F option   grep -F     Q amp    amp     amp        amp   amp    amp   amp   application log   Option -n is required to get the line number   grep -Fn     Q amp    amp     amp        amp   amp    amp   amp   application log

User · Answer

Try vi with the -b option  this will show special end of line characters  I typically use it to see windows line endings in a txt file on a unix OS   But if you want a scripted solution obviously vi wont work so you can try the -f or -e options with grep and pipe the result into sed or awk  From grep man page   Matcher Selection        -E  --extended-regexp               Interpret PATTERN as an extended regular expression  ERE  see below     -E is specified by POSIX       -F  --fixed-strings           Interpret PATTERN as a list of fixed strings  separated by newlines  any of which is to be matched    -F is specified           by POSIX

User · Answer

The one that worked for me is   grep -e  - gt     The -e means that the next argument is the pattern  and won t be interpreted as an argument   From  http   www linuxquestions org questions programming-9 how-to-grep-for-string-769460

User · Answer

A related note  To grep for carriage return  namely the  r character  or 0x0d  we can do this   grep -F    r  application log   Alternatively  use printf  or echo  for POSIX compatibility  grep -F    printf   r    application log   And we can use hexdump  or less to see the result     printf  a rb    grep -F    r    hexdump -c 0000000   a   r   b   n   Regarding the use of    r  and other supported characters  see Bash Manual   ANSI-C Quoting      Words of the form   string  are treated specially  The word expands to string  with backslash-escaped characters replaced as specified by the ANSI C standard

User · Answer

You could try removing any alphanumeric characters and space  And then use -n will give you the line number  Try following   grep -vn    a-zA-Z0-9      application log

User · Answer

grep -n         Q  amp     amp         amp           amp     amp     amp     amp   test log 1    Q amp   amp     amp      amp   amp   amp   amp  8    Q amp   amp     amp      amp   amp   amp   amp  14    Q amp   amp     amp      amp   amp   amp   amp

[unix] grep for special characters in Unix

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