The major one is the ability to nest them, commands within commands, without losing your sanity trying to figure out if some form of escaping will work on the backticks. An example, though somewhat contrived: deps=$(find /dir -name $(ls -1tr 201112[0-9][0-9]*.txt | tail -1l) -print) which will give you a list of all files in … Read more
You should use the = operator for string comparison: Sourcesystem=”ABC” if [ “$Sourcesystem” = “XYZ” ]; then echo “Sourcesystem Matched” else echo “Sourcesystem is NOT Matched $Sourcesystem” fi; man test says that you use -z to match for empty strings.
The -m option is probably what you’re looking for: grep -m 10 PATTERN [FILE] From man grep: -m NUM, –max-count=NUM Stop reading a file after NUM matching lines. If the input is standard input from a regular file, and NUM matching lines are output, grep ensures that the standard input is positioned to just after … Read more
/bin/sh is usually some other shell trying to mimic The Shell. Many distributions use /bin/bash for sh, it supports source. On Ubuntu, though, /bin/dash is used which does not support source. Most shells use . instead of source. If you cannot edit the script, try to change the shell which runs it.
In answer to your first question, there’s no parameter substitution because you’ve put the delimiter in quotes – the bash manual says: The format of here-documents is: <<[-]word here-document delimiter No parameter expansion, command substitution, arithmetic expansion, or pathname expansion is performed on word. If any characters in word are quoted, the delimiter is the … Read more
Addressing the question as updated. #…part of script without redirection… { #…part of script with redirection… } > file1 2>file2 # …and others as appropriate… #…residue of script without redirection… The braces ‘{ … }’ provide a unit of I/O redirection. The braces must appear where a command could appear – simplistically, at the start … Read more
echo -e $lines | while read line … done The while loop is executed in a subshell. So any changes you do to the variable will not be available once the subshell exits. Instead you can use a here string to re-write the while loop to be in the main shell process; only echo -e … Read more
Add a “shebang” at the top of your file: #!/bin/bash And make your file executable (chmod +x script.sh). Finally, modify your path to add the directory where your script is located: export PATH=$PATH:/appropriate/directory (typically, you want $HOME/bin for storing your own scripts)
You might want to look at the uniq and sort applications. ./yourscript.ksh | sort | uniq (FYI, yes, the sort is necessary in this command line, uniq only strips duplicate lines that are immediately after each other) EDIT: Contrary to what has been posted by Aaron Digulla in relation to uniq‘s commandline options: Given the … Read more
The backticks/gravemarks have been deprecated in favor of $() for command substitution because $() can easily nest within itself as in $(echo foo$(echo bar)). There are other differences such as how backslashes are parsed in the backtick/gravemark version, etc. See BashFAQ/082 for several reasons to always prefer the $(…) syntax. Also see the POSIX spec … Read more