Sponsored Content
Top Forums Shell Programming and Scripting How to understand special character for line reading in bash shell? Post 303039063 by RudiC on Saturday 21st of September 2019 02:24:23 PM
Old 09-21-2019
Not sure I'm an expert nor a guru, but this is what I'd do: refer to the respective man pages.
man bash:
Quote:
Parameter Expansion

${parameter#word}
${parameter##word}

Remove matching prefix pattern.


${parameter%word}
${parameter%%word}

Remove matching suffix pattern.



CONDITIONAL EXPRESSIONS.



An additional binary operator, =~, is available, with the same precedence as == and !=. When it is used, the string to the right of the operator is considered a POSIX extended regular expression and matched accordingly (as in regex(3))
Of course you need to learn the difference between shell's pattern matching and regex matching.

man regex:
Quote:
An atom is a regular expression ... '^' (matching the null string at the beginning of a line)

A bracket expression is a list of characters enclosed in "[]". It normally matches any single character from the list (but see below). If the list begins with '^', it matches any single character (but see below) not from the rest of the list.
Admittedly the ambiguous use of the caret is something you need to accustom to.
These 2 Users Gave Thanks to RudiC For This Post:
 

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

[OpenServer 5]Line Printing and special character (é @)

Hello, On Sco OpenServer 5, i want to print using the lpr command, no CUPS installed. I print on an HP LaserJet 4050 on LAN (IP 192.168.x.x) the printer is installed by HP Network Printer service. it works fine, but Specials characters, like é, @ or ° print bad characters. Is there... (5 Replies)
Discussion started by: tankd
5 Replies

2. Shell Programming and Scripting

bash shell: 'exec', 'eval', 'source' - looking for help to understand

Hi, experts. Whould anybody clear explay me difference and usage of these 3 commands (particulary in bash) : exec eval source I've tryed to read the manual pages but did not get much. Also could not get something useful from Google search - just so much and so not exactly, that is... (3 Replies)
Discussion started by: alex_5161
3 Replies

3. Shell Programming and Scripting

Adding a special character at the end of the line

I used following to add * at the end of the line in file1. It adds * at the end but has a space before it for some lines but some other lines it adds exactly after the last character. How do I take out the space ? sed 's/$/*/' file1 > file2 example: contents of file1 : ... (2 Replies)
Discussion started by: pitagi
2 Replies

4. Shell Programming and Scripting

How to insert a character in line in Special condition?

Hi, I have a log file generated by a tool which has the following look : /tmp/releases/directory/datefilename1_release_date.zip /tmp/releases/directory/datefilename2_release_date.zip /tmp/releases/directory/datefilename3_release_date.zip... (8 Replies)
Discussion started by: bhaskar_m
8 Replies

5. Shell Programming and Scripting

I need to understand the differences between the bash shell and the Bourne shell

I do not claim to be an expert, but I have done things with scripts that whole teams of folks have said can not be done. Of course they should have said we do not have the intestinal fortitude to git-r-done. I have been using UNIX actually HPUX since 1992. Unfortunately my old computer died and... (7 Replies)
Discussion started by: awk_sed_hello
7 Replies

6. Shell Programming and Scripting

Printing special character in bash

I am using this character as a delimiter 'þ' Currently, I set it straight: DELIMITER='þ' However, while copying the file, this character often gets mangled. Is there a bash way (perhaps using tr or printf) of generating this character. It corresponds to "chr(0xfe)" if using perl. (I've... (6 Replies)
Discussion started by: sentinel
6 Replies

7. Shell Programming and Scripting

parse special character in the line

Hi all, I have a file with some module names as below. Font::AFM Data::Grove ---> libxml-perl Net::LDAP ---> perl-ldap DBI XML .... ... .... and so on ... The file has some lines with the character " -->" . Now how can I cut only the last column of the line wherever "-->" is... (4 Replies)
Discussion started by: vijaya2006
4 Replies

8. UNIX for Dummies Questions & Answers

Reading character by character - BASH

Hello every one and thanks in advance for the time you will take to think about my problem. I would like to know if it's possible (in BASH) to read a text file character after character. Exactly this is what I would like to do : Txt file : ATGCAGTTCATTGCCAAA...... (~2.5 millions... (3 Replies)
Discussion started by: sluvah
3 Replies

9. Shell Programming and Scripting

Shell script question in special character

when I execute the unix commands its works normally in the 1st part. When I the tried the same in shell scripting the directory is not displayed in 2nd part example. please let me know what needs to be done. Unix : client=~zsvdbs echo $client /shome/zsvhome/zsvdbs Using... (3 Replies)
Discussion started by: keerthi2016
3 Replies

10. UNIX for Beginners Questions & Answers

Escape bash-special character in a bash string

Hi, I am new in bash scripting. In my work, I provide support to several users and when I connect to their computers I use the same admin and password, so I am trying to create a script that will only ask me for the IP address and then connect to the computer without having me to type the user... (5 Replies)
Discussion started by: arcoa05
5 Replies
MATCH(1L)						      Schily's USER COMMANDS							 MATCH(1L)

NAME
match - searches for patterns in files SYNOPSIS
match [ -option ] pattern [ file ... ] DESCRIPTION
Match searches the named files or standard input (if no filenames are given) for the occurrences of the given pattern on each line. The program accepts literal characters or special pattern matching characters. All lines that match the pattern are output on standard output. You can only specify one pattern string for each match, however, you can construct an arbitrarily complex string. When you do not specify a file, match can be used as a filter to display desired lines. Standard in is used if no files are specified. OPTIONS
-not, -v Prints all lines that do not match. -i Ignore the case of letters -m Force not to use the magic mode -w Search for pattern as a word -x Display only those lines which match exactly -c Display matching count for each file -l Display name of each file which matches -s Be silent indicate match in exit code -h Do not display filenames -n Precede matching lines with line number (with respect to the input file) -b Precede matching lines with block number REGULAR EXPRESSIONS
The following is a table of all the pattern matching characters: c An ordinary character (not one of the special characters discussed below) is a one character regular expression that matches that character. c A backslash () followed by any special character is a one character regular expression that matches the special character itself. The special characters are: ! # % * { } [ ] ? ^ $ ! Logical OR as in match this!that!the_other. You may have to use `{}' for precedence grouping. # A hash mark followed by any regular expression matches any number (including zero) occurrences of the regular expression. ? Matches exactly any one character. W? matches Wa, Wb, Wc, W1, W2, W3 ... * Matches any number of any character. % Matches exactly nothing. It can be used in groups of ored patterns to specify that an empty alternative is possible. {} Curly brackets may be used to enclose patterns to specify a precedence grouping, and may be nested. {%!{test}}version matches the strings testversion and version. [string] A non empty string of characters enclosed in square brackets is a one character regular expression that matches any one character in that string. If however the first character of the string is a circumflex (^), the one character expression matches any character which is not in the string. The ^ has this special meaning only if it occurs first in the string. The minus (-) may be used to indi- cate a range of consecutive ASCII characters; for example, [0-9] is equivalent to any one of the digits. The - loses it's special meaning if it occurs first (after an initial ^, if any) or last in the string. The right square bracket (]) and the backslash () must be quoted with a backslash if you want to use it within the string. ^ Matches the beginning of a line. $ Matches the end of a line. (^*$ matches any entire line) EXAMPLES
FILES
None. SEE ALSO
grep(1), fgrep(1), egrep(1) DIAGNOSTICS
NOTES
Even if a match occurs more than once per line, the line is output only once. Quote special pattern matching characters to prevent them from being expanded by the Command Interpreter. BUGS
The length of the pattern is currently limited to 100 characters. This limit is reduced by 38 if the -w option is used. Joerg Schilling 15. Juli 1988 MATCH(1L)
All times are GMT -4. The time now is 09:22 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy