Linux Commands 3

1
Linux Commands (3)

• Sudipto Das
• CS 60 Discussion
• Feb 16, 2007

Some points taken from http//www.oreillynet.com/l
inux/cmd/
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Contents

• source
• test
• cut
• find
• grep
• tar
• gzip and gunzip

3
source

• Usage source file arguments
• Read and execute the lines of a file.
• file does not need to be executable but must
  reside in a directory search by PATH
• Any arguments are passed as arguments to the file
  being executed
• The return status of the command is the return
  status of the last instruction executed in the
  file

4
test

• Usage test condition
• Evaluate a condition and, if the value is true,
  return 0, otherwise return a non zero exit status
• Condition can be constructed in a variety of ways
• File Conditions
• -a file file exists
• -d file file is a directory
• -e file file exists
• -f file file is regular
• -r file file is readable

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test

• String Conditions
• -n s1 String s1 has non zero length
• -z s1 String s1 has 0 length
• s1 s2 s1 and s2 are identical
• string string is not null
• Integer Comparisons
• n1 -eq n2 n1 equals n2
• n1 -ne n2 n1 does not equals n2
• n1 -gt n2 n1 greater than n2
• n1 -lt n2 n1 less than n2
• n1 -le n2 n1 less or equals n2

6
cut

• Usage cut options files
• Cut out selected columns or fields from one or
  more files.
• In the options, list is a sequence of integers.
• A comma is used between separate values, and a
  hyphen is used to specify a range.
• Options
• -d specify the delimiter
• -f specify the field to cut
• -c specify the column number

7
find

• Usage find pathnames conditions
• An extremely useful command for finding
  particular groups of files (numerous examples
  follow this description).
• find descends the directory tree beginning at
  each pathname and locates files that meet the
  specified conditions.
• The default pathname is the current directory
• The most useful conditions include
• -name and -type (for general use),
• -exec and -size (for advanced use), and
• -mtime and -user (for administrators).

8
grep

• Usage grep options pattern files
• Search one or more files for lines that match a
  regular expression pattern
• Options
• -a Don't suppress output lines with binary
  data, treat as text.
• -c Print only a count of matched lines. With -v
  option, count non-matching lines
• -e pattern search for the pattern in the file
• -n print the line numbers with the matching
  lines
• -r search recursively
• -v invert matches

9
tar

• Usage tar options tarfile other-files
• Copy files to or restore files from an archive
  medium.
• If any of files are directories, tar acts on the
  entire subtree
• Options
• -c create an archive
• -x extract an archive
• -v verbose
• -r append at the end of an existing archive
• -z use gzip while archiving or extracting

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gzip and gunzip

• Usage
• gzip options files
• gunzip options files
• Zip or unzip the files.
• Options
• -v verbose
• -r recursive
• -f force zipping or unzipping

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Pipelining Commands

• Output of one command becomes the input of the
  next command
• Pipelining done by using the operator
• Use the power of Linux commands to do great jobs