can't get specific line from bash output
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0
down vote
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I'm trying simple bash script:
/usr/libexec/java_home -V
output is:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
Seems to be 4 lines, but if I try to get second line:
/usr/libexec/java_home -V | sed -n 2p
The output is the same. No additional line. If I try the first one - I got the second:
/usr/libexec/java_home -V | sed -n 1p
Output:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
If I assign output to array and count it's size:
array=( $(/usr/libexec/java_home -V) )
array_size=$#array[@]
echo $array_size
it shows size = 1:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
1
What am I doing wrong?
bash stdout stderr io-redirection
edited Nov 11 at 0:43
Cyrus
44.9k43676
asked Nov 11 at 0:10
Iga
335
add a comment |
up vote
0
down vote
favorite
I'm trying simple bash script:
/usr/libexec/java_home -V
output is:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
Seems to be 4 lines, but if I try to get second line:
/usr/libexec/java_home -V | sed -n 2p
The output is the same. No additional line. If I try the first one - I got the second:
/usr/libexec/java_home -V | sed -n 1p
Output:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
If I assign output to array and count it's size:
array=( $(/usr/libexec/java_home -V) )
array_size=$#array[@]
echo $array_size
it shows size = 1:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
1
What am I doing wrong?
bash stdout stderr io-redirection
edited Nov 11 at 0:43
Cyrus
44.9k43676
asked Nov 11 at 0:10
Iga
335
3
Likely output is tostderrinstead ofstdout, Try/usr/libexec/java_home -V 2>&1 | sed -n 1pPossible the"Matching Java.."is tostdoutand the rest tostderr. (hard to tell). You can always use/usr/libexec/java_home -V 2>/dev/nullto eliminate what is output tostderrto test. If it is all tostdout, then there is something preventing normal word-splitting from occurring. Have you alteredIFSin your parent shell?
– David C. Rankin
Nov 11 at 0:16
/usr/libexec/java_home -V 2>&1 | sed -n 1pworks nice! Thank you!
– Iga
Nov 11 at 0:34
Sure, glad it helped. Yoursedcall was correct, so the only other likely cause was the script was outputting tostderr(which isn't being piped tosedand just appears on your screen making it look likesedwasn't working). Now you know what to look for when something like that pops up -- we have all learned that lesson the same way:)
– David C. Rankin
Nov 11 at 0:40
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
I'm trying simple bash script:
/usr/libexec/java_home -V
output is:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
Seems to be 4 lines, but if I try to get second line:
/usr/libexec/java_home -V | sed -n 2p
The output is the same. No additional line. If I try the first one - I got the second:
/usr/libexec/java_home -V | sed -n 1p
Output:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
If I assign output to array and count it's size:
array=( $(/usr/libexec/java_home -V) )
array_size=$#array[@]
echo $array_size
it shows size = 1:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
1
What am I doing wrong?
bash stdout stderr io-redirection
edited Nov 11 at 0:43
Cyrus
44.9k43676
asked Nov 11 at 0:10
Iga
335
I'm trying simple bash script:
/usr/libexec/java_home -V
output is:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
Seems to be 4 lines, but if I try to get second line:
/usr/libexec/java_home -V | sed -n 2p
The output is the same. No additional line. If I try the first one - I got the second:
/usr/libexec/java_home -V | sed -n 1p
Output:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
If I assign output to array and count it's size:
array=( $(/usr/libexec/java_home -V) )
array_size=$#array[@]
echo $array_size
it shows size = 1:
Matching Java Virtual Machines (3):
11.0.1, x86_64: "Java SE 11.0.1" /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
10.0.1, x86_64: "Java SE 10.0.1" /Library/Java/JavaVirtualMachines/jdk-10.0.1.jdk/Contents/Home
1.8.0_192, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
1
What am I doing wrong?
bash stdout stderr io-redirection
bash stdout stderr io-redirection
edited Nov 11 at 0:43
Cyrus
44.9k43676
asked Nov 11 at 0:10
Iga
335
edited Nov 11 at 0:43
Cyrus
44.9k43676
asked Nov 11 at 0:10
Iga
335
edited Nov 11 at 0:43
Cyrus
44.9k43676
edited Nov 11 at 0:43
Cyrus
44.9k43676
edited Nov 11 at 0:43
Cyrus
44.9k43676
44.9k43676
asked Nov 11 at 0:10
Iga
335
asked Nov 11 at 0:10
Iga
335
asked Nov 11 at 0:10
Iga
335
335
3
Likely output is tostderrinstead ofstdout, Try/usr/libexec/java_home -V 2>&1 | sed -n 1pPossible the"Matching Java.."is tostdoutand the rest tostderr. (hard to tell). You can always use/usr/libexec/java_home -V 2>/dev/nullto eliminate what is output tostderrto test. If it is all tostdout, then there is something preventing normal word-splitting from occurring. Have you alteredIFSin your parent shell?
– David C. Rankin
Nov 11 at 0:16
/usr/libexec/java_home -V 2>&1 | sed -n 1pworks nice! Thank you!
– Iga
Nov 11 at 0:34
Sure, glad it helped. Yoursedcall was correct, so the only other likely cause was the script was outputting tostderr(which isn't being piped tosedand just appears on your screen making it look likesedwasn't working). Now you know what to look for when something like that pops up -- we have all learned that lesson the same way:)
– David C. Rankin
Nov 11 at 0:40
add a comment |
3
Likely output is tostderrinstead ofstdout, Try/usr/libexec/java_home -V 2>&1 | sed -n 1pPossible the"Matching Java.."is tostdoutand the rest tostderr. (hard to tell). You can always use/usr/libexec/java_home -V 2>/dev/nullto eliminate what is output tostderrto test. If it is all tostdout, then there is something preventing normal word-splitting from occurring. Have you alteredIFSin your parent shell?
– David C. Rankin
Nov 11 at 0:16
/usr/libexec/java_home -V 2>&1 | sed -n 1pworks nice! Thank you!
– Iga
Nov 11 at 0:34
Sure, glad it helped. Yoursedcall was correct, so the only other likely cause was the script was outputting tostderr(which isn't being piped tosedand just appears on your screen making it look likesedwasn't working). Now you know what to look for when something like that pops up -- we have all learned that lesson the same way:)
– David C. Rankin
Nov 11 at 0:40
3
3
Likely output is to
stderr instead of stdout, Try /usr/libexec/java_home -V 2>&1 | sed -n 1p Possible the "Matching Java.." is to stdout and the rest to stderr. (hard to tell). You can always use /usr/libexec/java_home -V 2>/dev/null to eliminate what is output to stderr to test. If it is all to stdout, then there is something preventing normal word-splitting from occurring. Have you altered IFS in your parent shell?– David C. Rankin
Nov 11 at 0:16
Likely output is to
stderr instead of stdout, Try /usr/libexec/java_home -V 2>&1 | sed -n 1p Possible the "Matching Java.." is to stdout and the rest to stderr. (hard to tell). You can always use /usr/libexec/java_home -V 2>/dev/null to eliminate what is output to stderr to test. If it is all to stdout, then there is something preventing normal word-splitting from occurring. Have you altered IFS in your parent shell?– David C. Rankin
Nov 11 at 0:16
/usr/libexec/java_home -V 2>&1 | sed -n 1p works nice! Thank you!– Iga
Nov 11 at 0:34
/usr/libexec/java_home -V 2>&1 | sed -n 1p works nice! Thank you!– Iga
Nov 11 at 0:34
Sure, glad it helped. Your
sed call was correct, so the only other likely cause was the script was outputting to stderr (which isn't being piped to sed and just appears on your screen making it look like sed wasn't working). Now you know what to look for when something like that pops up -- we have all learned that lesson the same way :)– David C. Rankin
Nov 11 at 0:40
Sure, glad it helped. Your
sed call was correct, so the only other likely cause was the script was outputting to stderr (which isn't being piped to sed and just appears on your screen making it look like sed wasn't working). Now you know what to look for when something like that pops up -- we have all learned that lesson the same way :)– David C. Rankin
Nov 11 at 0:40
add a comment |
1 Answer
1
active
oldest
votes
up vote
1
down vote
accepted
What appears to be happening is that your script, /usr/libexec/java_home -V is outputting some, or all, of its output to stderr instead of writing to stdout. Since the shell pipe ('|') connects the stdout of the previous command to stdin of the command that follows, any output to stderr by /usr/libexec/java_home -V just gets written to your screen and is never processed by sed making it look like sed wasn't working.
To test and correct the problem is that is the case, just redirect stderr from your script to stdout and then pipe the result to sed, making sure sed receives all of the output from your script, e.g.
$ /usr/libexec/java_home -V 2>&1 | sed -n 1p
Glad it helped.
answered Nov 11 at 0:46
David C. Rankin
39.9k32647
add a comment |
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1 Answer
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oldest
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oldest
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oldest
votes
up vote
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down vote
accepted
What appears to be happening is that your script, /usr/libexec/java_home -V is outputting some, or all, of its output to stderr instead of writing to stdout. Since the shell pipe ('|') connects the stdout of the previous command to stdin of the command that follows, any output to stderr by /usr/libexec/java_home -V just gets written to your screen and is never processed by sed making it look like sed wasn't working.
To test and correct the problem is that is the case, just redirect stderr from your script to stdout and then pipe the result to sed, making sure sed receives all of the output from your script, e.g.
$ /usr/libexec/java_home -V 2>&1 | sed -n 1p
Glad it helped.
answered Nov 11 at 0:46
David C. Rankin
39.9k32647
add a comment |
up vote
1
down vote
accepted
What appears to be happening is that your script, /usr/libexec/java_home -V is outputting some, or all, of its output to stderr instead of writing to stdout. Since the shell pipe ('|') connects the stdout of the previous command to stdin of the command that follows, any output to stderr by /usr/libexec/java_home -V just gets written to your screen and is never processed by sed making it look like sed wasn't working.
To test and correct the problem is that is the case, just redirect stderr from your script to stdout and then pipe the result to sed, making sure sed receives all of the output from your script, e.g.
$ /usr/libexec/java_home -V 2>&1 | sed -n 1p
Glad it helped.
answered Nov 11 at 0:46
David C. Rankin
39.9k32647
add a comment |
up vote
1
down vote
accepted
up vote
1
down vote
accepted
What appears to be happening is that your script, /usr/libexec/java_home -V is outputting some, or all, of its output to stderr instead of writing to stdout. Since the shell pipe ('|') connects the stdout of the previous command to stdin of the command that follows, any output to stderr by /usr/libexec/java_home -V just gets written to your screen and is never processed by sed making it look like sed wasn't working.
To test and correct the problem is that is the case, just redirect stderr from your script to stdout and then pipe the result to sed, making sure sed receives all of the output from your script, e.g.
$ /usr/libexec/java_home -V 2>&1 | sed -n 1p
Glad it helped.
answered Nov 11 at 0:46
David C. Rankin
39.9k32647
What appears to be happening is that your script, /usr/libexec/java_home -V is outputting some, or all, of its output to stderr instead of writing to stdout. Since the shell pipe ('|') connects the stdout of the previous command to stdin of the command that follows, any output to stderr by /usr/libexec/java_home -V just gets written to your screen and is never processed by sed making it look like sed wasn't working.
To test and correct the problem is that is the case, just redirect stderr from your script to stdout and then pipe the result to sed, making sure sed receives all of the output from your script, e.g.
$ /usr/libexec/java_home -V 2>&1 | sed -n 1p
Glad it helped.
answered Nov 11 at 0:46
David C. Rankin
39.9k32647
answered Nov 11 at 0:46
David C. Rankin
39.9k32647
answered Nov 11 at 0:46
David C. Rankin
39.9k32647
answered Nov 11 at 0:46
David C. Rankin
39.9k32647
39.9k32647
add a comment |
add a comment |
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3
Likely output is to
stderrinstead ofstdout, Try/usr/libexec/java_home -V 2>&1 | sed -n 1pPossible the"Matching Java.."is tostdoutand the rest tostderr. (hard to tell). You can always use/usr/libexec/java_home -V 2>/dev/nullto eliminate what is output tostderrto test. If it is all tostdout, then there is something preventing normal word-splitting from occurring. Have you alteredIFSin your parent shell?– David C. Rankin
Nov 11 at 0:16
/usr/libexec/java_home -V 2>&1 | sed -n 1pworks nice! Thank you!– Iga
Nov 11 at 0:34
Sure, glad it helped. Your
sedcall was correct, so the only other likely cause was the script was outputting tostderr(which isn't being piped tosedand just appears on your screen making it look likesedwasn't working). Now you know what to look for when something like that pops up -- we have all learned that lesson the same way:)– David C. Rankin
Nov 11 at 0:40