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Merge pull request #839 from westurner/patch-1

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[bash/en] add bash redirection examples
This commit is contained in:
Levi Bostian 2014-11-01 13:36:53 -05:00
commit 24a4426dd0
1 changed files with 39 additions and 6 deletions
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@ -111,12 +111,45 @@ ls -l # Lists every file and directory on a separate line
# .txt files in the current directory: # .txt files in the current directory:
ls -l | grep "\.txt" ls -l | grep "\.txt"
# You can also redirect a command, input and error output. # You can redirect command input and output (stdin, stdout, and stderr).
python2 hello.py < "input.in" # Read from stdin until ^EOF$ and overwrite hello.py with the lines
python2 hello.py > "output.out" # between "EOF":
python2 hello.py 2> "error.err" cat > hello.py << EOF
# The output error will overwrite the file if it exists, if you want to #!/usr/bin/env python
# concatenate them, use ">>" instead. from __future__ import print_function
import sys
print("#stdout", file=sys.stdout)
print("#stderr", file=sys.stderr)
for line in sys.stdin:
print(line, file=sys.stdout)
EOF
# Run hello.py with various stdin, stdout, and stderr redirections:
python hello.py < "input.in"
python hello.py > "output.out"
python hello.py 2> "error.err"
python hello.py > "output-and-error.log" 2>&1
python hello.py > /dev/null 2>&1
# The output error will overwrite the file if it exists,
# if you want to append instead, use ">>":
python hello.py >> "output.out" 2>> "error.err"
# Overwrite output.txt, append to error.err, and count lines:
info bash 'Basic Shell Features' 'Redirections' > output.out 2>> error.err
wc -l output.out error.err
# Run a command and print its file descriptor (e.g. /dev/fd/123)
# see: man fd
echo <(echo "#helloworld")
# Overwrite output.txt with "#helloworld":
cat > output.out <(echo "#helloworld")
echo "#helloworld" > output.out
echo "#helloworld" | cat > output.out
echo "#helloworld" | tee output.out >/dev/null
# Cleanup temporary files verbosely (add '-i' for interactive)
rm -v output.out error.err output-and-error.log
# Commands can be substituted within other commands using $( ): # Commands can be substituted within other commands using $( ):
# The following command displays the number of files and directories in the # The following command displays the number of files and directories in the