Sponsored Content
Top Forums Shell Programming and Scripting Sed insert text at first line of empty file Post 302497757 by DC Slick on Friday 18th of February 2011 02:17:58 AM
Old 02-18-2011
I don't want to use echo because I want the first line to be a comment, and the rest to be values that a script reads from. If the user deletes the commented line like they're not supposed to, i want the script not to fail and to replace the line. I want sed to say:
Code:
 sed -i 's/^$/#CUSTOM/' infile

but only to the first line. I don't want #CUSTOM to be all over the place where there's new lines.

my commands go in order: touch infile; sed (add #CUSTOM to beginning of this file). I don't want each iteration of the script to add #CUSTOM to the beginning. ONLY if line one is empty or does not contain #CUSTOM
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

SED- Insert text at top of file

Does anyone know how to insert text at the top and bottom of a file using sed? (12 Replies)
Discussion started by: MBGPS
12 Replies

2. Shell Programming and Scripting

How to insert some constant text at beginig of each line within a text file.

Dear Folks :), I am new to UNIX scripting and I do not know how can I insert some text in the first column of a UNIX text file at command promtp. I can do this in vi editor by using this command :g/^/s//BBB_ e,g I have a file named as Test.dat and it containins below text: michal... (4 Replies)
Discussion started by: Muhammad Afzal
4 Replies

3. Shell Programming and Scripting

Need to insert new text and change existing text in a file using SED

Hi all, I need to insert new text and change existing text in a file. For that I used the below line in the command line and got the expected output. sed '$a\ hi... ' shell > shell1 But I face problem when using the same in script. It is throwing the error as, sed: command garbled:... (4 Replies)
Discussion started by: iamgeethuj
4 Replies

4. Shell Programming and Scripting

sed insert text at particular line

I know that sed -n '12p' file will print line 12 but how might I insert text to a specified line? thanks (2 Replies)
Discussion started by: action_owl
2 Replies

5. Shell Programming and Scripting

Using sed to insert text file at first line

sed '1r file.txt' <source.txt >desti.txt This example will insert 'file.txt' between line 1 and 2 of source.txt. sed '0r file.txt' <source.txt >desti.txt gives an error message. Does anyone know how 'sed' can insert 'file.txt' before the first line of source.txt? (18 Replies)
Discussion started by: psve
18 Replies

6. Shell Programming and Scripting

Delete the last empty/blank line of the text file

Hi All, I have a file.txt which seems like having three lines. wc -l file.txt 3 file.txt In fact, once it is open in text editor, this file has four lines where the last line is empty. how can i delete this last empty line of the file.txt? I tried the codes below so far but they... (6 Replies)
Discussion started by: senayasma
6 Replies

7. Shell Programming and Scripting

insert text into empty file

I have an awk script to extract data from several files and create output in the following format as a csv file: xxxx 01/04/12 0001 0 When data is present, I have a file. When no data is available in the input files, I would still like to create a file that looks like this: xxxx... (1 Reply)
Discussion started by: banjo25
1 Replies

8. Shell Programming and Scripting

sed - insert text if column empty

Hi, I want to insert the text 'Unknown' in 2 specific columns in a csv file (actually | separated) if the column is blank. Its always the same columns. I have tried using sed: sed "s/||/|Unknown|/g" but there are occasion where other fields are blank and they need to be left blank. This... (4 Replies)
Discussion started by: ksexton
4 Replies

9. Shell Programming and Scripting

How to read a text file line by line and insert into a database table?

I have a test file that I want to read and insert only certain lines into the the table based on a filter. 1. Rread the log file 12 Hours back Getdate() -12 Hours 2. Extract the following information on for lines that say "DUMP is complete" A. Date B. Database Name C.... (2 Replies)
Discussion started by: JolietJake
2 Replies

10. UNIX for Beginners Questions & Answers

Insert a line of text on nth line of a file

Hi All, I am using UNix Sun OS sun4u sparc SUNW,SPARC-Enterprise My intention is to insert a line of text after 13th line of every file inside a particular directory. While trying to do it for a single file , i am using sed sed '3 i this is the 4th line' filename sed: command garbled: 3... (5 Replies)
Discussion started by: gotamp
5 Replies
SED(1)                                                             User Commands                                                            SED(1)

NAME
sed - stream editor for filtering and transforming text SYNOPSIS
sed [OPTION]... {script-only-if-no-other-script} [input-file]... DESCRIPTION
Sed is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipe- line). While in some ways similar to an editor which permits scripted edits (such as ed), sed works by making only one pass over the input(s), and is consequently more efficient. But it is sed's ability to filter text in a pipeline which particularly distinguishes it from other types of editors. -n, --quiet, --silent suppress automatic printing of pattern space -e script, --expression=script add the script to the commands to be executed -f script-file, --file=script-file add the contents of script-file to the commands to be executed --follow-symlinks follow symlinks when processing in place -i[SUFFIX], --in-place[=SUFFIX] edit files in place (makes backup if SUFFIX supplied) -l N, --line-length=N specify the desired line-wrap length for the `l' command --posix disable all GNU extensions. -E, -r, --regexp-extended use extended regular expressions in the script (for portability use POSIX -E). -s, --separate consider files as separate rather than as a single, continuous long stream. --sandbox operate in sandbox mode. -u, --unbuffered load minimal amounts of data from the input files and flush the output buffers more often -z, --null-data separate lines by NUL characters --help display this help and exit --version output version information and exit If no -e, --expression, -f, or --file option is given, then the first non-option argument is taken as the sed script to interpret. All remaining arguments are names of input files; if no input files are specified, then the standard input is read. GNU sed home page: <http://www.gnu.org/software/sed/>. General help using GNU software: <http://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-sed@gnu.org>. COMMAND SYNOPSIS
This is just a brief synopsis of sed commands to serve as a reminder to those who already know sed; other documentation (such as the tex- info document) must be consulted for fuller descriptions. Zero-address ``commands'' : label Label for b and t commands. #comment The comment extends until the next newline (or the end of a -e script fragment). } The closing bracket of a { } block. Zero- or One- address commands = Print the current line number. a text Append text, which has each embedded newline preceded by a backslash. i text Insert text, which has each embedded newline preceded by a backslash. q [exit-code] Immediately quit the sed script without processing any more input, except that if auto-print is not disabled the current pattern space will be printed. The exit code argument is a GNU extension. Q [exit-code] Immediately quit the sed script without processing any more input. This is a GNU extension. r filename Append text read from filename. R filename Append a line read from filename. Each invocation of the command reads a line from the file. This is a GNU extension. Commands which accept address ranges { Begin a block of commands (end with a }). b label Branch to label; if label is omitted, branch to end of script. c text Replace the selected lines with text, which has each embedded newline preceded by a backslash. d Delete pattern space. Start next cycle. D If pattern space contains no newline, start a normal new cycle as if the d command was issued. Otherwise, delete text in the pat- tern space up to the first newline, and restart cycle with the resultant pattern space, without reading a new line of input. h H Copy/append pattern space to hold space. g G Copy/append hold space to pattern space. l List out the current line in a ``visually unambiguous'' form. l width List out the current line in a ``visually unambiguous'' form, breaking it at width characters. This is a GNU extension. n N Read/append the next line of input into the pattern space. p Print the current pattern space. P Print up to the first embedded newline of the current pattern space. s/regexp/replacement/ Attempt to match regexp against the pattern space. If successful, replace that portion matched with replacement. The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes 1 through 9 to refer to the corresponding matching sub-expressions in the regexp. t label If a s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script. T label If no s/// has done a successful substitution since the last input line was read and since the last t or T command, then branch to label; if label is omitted, branch to end of script. This is a GNU extension. w filename Write the current pattern space to filename. W filename Write the first line of the current pattern space to filename. This is a GNU extension. x Exchange the contents of the hold and pattern spaces. y/source/dest/ Transliterate the characters in the pattern space which appear in source to the corresponding character in dest. Addresses Sed commands can be given with no addresses, in which case the command will be executed for all input lines; with one address, in which case the command will only be executed for input lines which match that address; or with two addresses, in which case the command will be executed for all input lines which match the inclusive range of lines starting from the first address and continuing to the second address. Three things to note about address ranges: the syntax is addr1,addr2 (i.e., the addresses are separated by a comma); the line which addr1 matched will always be accepted, even if addr2 selects an earlier line; and if addr2 is a regexp, it will not be tested against the line that addr1 matched. After the address (or address-range), and before the command, a ! may be inserted, which specifies that the command shall only be executed if the address (or address-range) does not match. The following address types are supported: number Match only the specified line number (which increments cumulatively across files, unless the -s option is specified on the command line). first~step Match every step'th line starting with line first. For example, ``sed -n 1~2p'' will print all the odd-numbered lines in the input stream, and the address 2~5 will match every fifth line, starting with the second. first can be zero; in this case, sed operates as if it were equal to step. (This is an extension.) $ Match the last line. /regexp/ Match lines matching the regular expression regexp. cregexpc Match lines matching the regular expression regexp. The c may be any character. GNU sed also supports some special 2-address forms: 0,addr2 Start out in "matched first address" state, until addr2 is found. This is similar to 1,addr2, except that if addr2 matches the very first line of input the 0,addr2 form will be at the end of its range, whereas the 1,addr2 form will still be at the beginning of its range. This works only when addr2 is a regular expression. addr1,+N Will match addr1 and the N lines following addr1. addr1,~N Will match addr1 and the lines following addr1 until the next line whose input line number is a multiple of N. REGULAR EXPRESSIONS
POSIX.2 BREs should be supported, but they aren't completely because of performance problems. The sequence in a regular expression matches the newline character, and similarly for a, , and other sequences. The -E option switches to using extended regular expressions instead; the -E option has been supported for years by GNU sed, and is now included in POSIX. BUGS
E-mail bug reports to bug-sed@gnu.org. Also, please include the output of ``sed --version'' in the body of your report if at all possible. AUTHOR
Written by Jay Fenlason, Tom Lord, Ken Pizzini, and Paolo Bonzini. GNU sed home page: <http://www.gnu.org/software/sed/>. General help using GNU software: <http://www.gnu.org/gethelp/>. E-mail bug reports to: <bug-sed@gnu.org>. COPYRIGHT
Copyright (C) 2017 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO
awk(1), ed(1), grep(1), tr(1), perlre(1), sed.info, any of various books on sed, the sed FAQ (http://sed.sf.net/grabbag/tutorials/sed- faq.txt), http://sed.sf.net/grabbag/. The full documentation for sed is maintained as a Texinfo manual. If the info and sed programs are properly installed at your site, the command info sed should give you access to the complete manual. sed 4.4 February 2017 SED(1)
All times are GMT -4. The time now is 10:34 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy